This is easily cured with antibiotics such as Penicillin. Your foal will not have received any vaccination shots or deworming. All foals get worms and it is important to deworm them regularly. Have your vet determine a good time to deworm and vaccinate your foal. You will receive a negative Coggin's test when you retrieve your foal.
Males usually reach sexual maturity from one to two years of age but sometimes sooner.
If you plan on housing your colt with mares, you may want to consider getting him castrated sooner rather than later. Again, check with your vet. However, when these foals come to the sales, they are herded from pen to pen, chute to chute, and from trailer to trailer. They learn that every time they come in contact with a human they are to go in the opposite direction. Some may be more skittish than others but with a little time and a lot of patience they will quickly bond with you.