Well first, its not going to get well as long as you keep
Chewing on it. Mouth sores are usually cause by the herpes virus which lives on every human naturally, not just dirty ones, and most often causes no problems. However when it flares up as a cold sore or mouth ulcer its a high contageous infection. Chewing on it only makes it worse. It may have begun from accidentally biting you lip or some food that cause a cut. STOP chewing on it, use a salt brine gargle on it (do NOT swallow the brine). Dont share cups or bottles or eating utensils or food with anyone. Everything your mouth touches needs to be washed in HOT water, try not to touch your mouth with your hands and if you do wash them immediately. Most of all STOP CHEWING ON IT!!! Worst. Thing. Ever. If it doesnt go away in a few days you may need to get it treated.