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Thomas, one of leader Chris Froome's key helpers in the mountains, fell and broke his collarbone on the descent of the Col de la Biche during stage nine.
The Team Sky rider, 31, also crashed out on stage nine of the Giro d'Italia.
"It's still quite raw, the emotions of it all," the Welshman said. "I'm sure it will hit me when I go home and realise I'm not in the race any more."
Thomas, who has finished 15th in the Tour de France the past two years, won the opening 14km time trial this year in Dusseldorf and was second overall when he crashed on Sunday.
"It's been tough because I've worked so hard recently and felt like in the Giro that I was in really top shape - and obviously what happened there happened and through no fault of my own," he told BBC Sport.
"Here is one of the highlights of my career really - winning a stage and yellow jersey for so long - and then for it to end like that it's a bitter pill to swallow.
"Rafal Majka was trying to get past me a while, then he slapped on [the brakes] right in front of me, literally 10 seconds after I let him past. I was on his wheel doing 60km/h an hour, there's absolutely nowhere to go. [Matteo] Trentin came down as well and it was just carnage really."
Asked if Team Sky could protect fellow Briton Froome's 18-second advantage, he added: "The boys are still super strong, mentally as much as physically. They're a real good group and they'll really pull together now. I've got every confidence that they'll be able to do the job with Froomey."
Thomas, who will be seeing a specialist about his injury in Cardiff on Tuesday, said he will have an operation as soon as possible.
"I'll be able to go back on the bike really soon," he said. "Goals-wise I don't know. I'll leave it a week, let the dust settle and decide what will motivate me until the end of the season.
"At the moment I just want to go down the pub."
Thomas' former Team Sky team-mate Richie Porte says he hopes to return to racing before the end of the season after a high-speed crash during stage nine ended his hopes in the Tour.
The Australian Team BMC rider has spoken from his hospital bed after suffering a broken collarbone and pelvis.
"I'm in a fair bit of pain and it's a big disappointment," Porte said in a video released on his team's Facebook page.
"I was in great form and the team were really strong around me as well, so it's disappointing - but I think after seeing the crash I'm lucky also that I walked away with the injuries that I have."
Porte, who was one of the pre-race favourites, was taken by ambulance from the course in a neck brace.
"I don't think I'll be back on my bike for a good while now. The team's good with that, they say 'just recover, there's no rush to come back' and hopefully I'll pull the BMC jersey on by the end of the year."
On his recollection of the crash, the 32-year-old added: "I remember I came into the corner, it wasn't like we were going too fast or anything like that, but I just remember I locked the back wheel up and that was it really.
"The next thing I was heading for the grass verge on the corner. I stayed conscious the whole time, I remember the whole thing.
"I must say thank you to the medical staff in the race and also in the hospital, they've been absolutely fantastic."
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Summarize: Britain's Geraint Thomas says being forced out of the Tour de France by injury is "a bitter pill to swallow".


Problem: The 53-year-old is keen to add to the squad to aid their League Two promotion bid, following back-to-back defeats at the start of 2017.
United are third in the table, six points behind leaders Doncaster having lost just three games in total.
"We're close to capacity," Curle told BBC Radio Cumbria.
"We're at a stage where we need to get players off the wage bill to bring players in.
"It's a different part of my job now where it's not [training] field based, it's office based where I need to move players on to bring players in."
United have already extended the loan of Newcastle defender Macaulay Gillesphey until the end of the season, a deal Curle says required a "re-jigging of figures presented to the Football League" to ensure the deal could go through under terms of the salary cap.
Short-term deals have also been given to defenders Kevin Wright and Alexander McQueen.
What was that article about?

A: Carlisle United's January transfer window additions are likely to be dependent on players leaving Brunton Park, says manager Keith Curle.


Problem: The 25-year-old injured her foot in March, ending her hopes of defending the ITU World Championships title she won in 2013.
But while her running has been affected Stanford has still been able to train normally on the bike and in the pool.
"I'm still coming back from that injury," Stanford said.
"We're really working towards being fit and ready for Glasgow and not much before that.
My mother has been involved in the Commonwealth Games in the past, so I'm really excited to go and finally represent Wales
"It's dragged on a bit longer than I'd hoped but... it's all part of the challenge and I've got the best medical team around me, the same team that got [London 2012 gold medal winner] Alistair Brownlee on his feet and ready for the Olympics.
"Hopefully we'll get it right and I'll be all guns blazing in Glasgow.
"It really limits the amount of running I can do; it's a foot injury so it does mean my running has to be very graded and we're really being cautious around it.
"But I've been able to ride and swim now for a while and I'm feeling really strong in both of them, so hopefully the running will come back quickly because I'm pretty fit anyway."
Stanford will form a strong Wales women's team with 2011 world champion Helen Jenkins and Holly Lawrence, who was preferred by the selectors to Ironman world champion Leanda Cave.
Morgan Davies, Liam Lloyd and Alex Matchett make up the men's team for Glasgow 2014.
Stanford revealed that her inclusion to compete at a Commonwealth Games will fulfil one of her childhood dreams.
"It's been a life-long ambition to represent Wales at the Commonwealth Games - it came on to my radar long before the Olympics and when I was a child it was my first memory of a major sporting event," Stanford said.
"My mother has been involved in the Commonwealth Games in the past, so I'm really excited to go and finally represent Wales.
"My mum was involved in gymnastics as I was growing up and she coached the Welsh gymnasts and was one of the judges that went along as part of Team Wales to Kuala Lumpur [1998 Games].
"I can remember her going and being really excited and it'll be great now to be part of that myself."
What was that article about?

A:

assistant: Wales triathlete Non Stanford admits her build-up for the 2014 Commonwealth Games is still being hampered by a long-term injury.