I agree with Lady of McCamley that it could be fowl pox, which is carried by mosquitoes in hot weather. There is also a type of bump that is seen on chick's faces especially around the beak sometimes that may be due to an injury on sharp objects, or possible from a papillovirus. If you do a search BYC forums for "wart or sore on beak" you may find info on that. But it may well be pox, and that usually lasts for several weeks. Make sure that the chicken is eating and drinking well, since there is a wet form of pox that affects the throat.