Nicolas' first races at the senior level were the last two World Cups of the 2018 season where he made both finals finishing 8th and 10th in Tacen and La Seu, respectively. He won a silver medal at the 2020 World Cup in Tacen. Gestin was coached by 1993 and 1995 vice world champion Anne Boixel until 2021 and now by French national team coach Arnaud Brogniart. He participated in the French selection trials for the 2020 Summer Olympics, finishing 6th. Gestin finished 5th at the 2021 European Championships in Ivrea.