i don't know that age of your son but stomatitis is only in the mouth but if he is also having blister-like lesions appearing on his hands and the bottom of his feet i would be highly suspicious that he has hand foot and mouth disease (a coxsakie virus infection).
can stomatitis appear on hands? . my son is very sick they say it is stomatitis he has infected thumb and two other fingers are infected as well is this normal with stomatitis?