They're called apthous ulcers. They are benign, non-contagious mouth ulcer. Usually due to either biting the area, lack of sleep, poor diet, eating spicy food or crunchy abrasive food. They reoccur every now and then and can last a couple weeks. I've had this where they formed on my tonsils as well. This looks to be a very small/minimally painful case. The fist time I had them on my tonsils, my tonsils were litterally covered with them. You couldn't see them, just white ulcers. And that shit HURT, BAD. Imagine having open soars in your throat and every time you simply swallow the residual saliva in your mouth it hurts like a MOTHER FUCKER. No it's not strepp so tell your doctor hes a moron like my doctor was.