Get that tooth extracted. Do not delay. Chronic irritation to gum may lead to life threatening  conditions.

It is traumatic ulcer caused by wisdom tooth. Its not healing because of continuous irritation caused by third molar. Best treatment is extraction of upper wisdom tooth.

Better extract that tooth wch is impinging n ur cheeks.. The same issue won't resolve even if u try to smooth the tooth

Hello , it seems to be traumatic ulcer  due to cusp of wisdom tooth impinging in that region . Also want to know ow how long this ulcer is ?? First of all visit a dentist and get the cusps  of ur upper and lower wisdom teeth  smothened.  Local application of mucopain on d ulcer and vit c tabs for 8 days . If still  the ulcer persists then u can contact on my personal chat will guide u further  . I m an Oral Medicine and radiologist  and deals with such cases . But advice u to c a nearby dentist immediately  and get smothening of sharp cusps and  give a follow up after 8 to 10 days with the pictures.

Hello, from the picture it looks like it is because of the position of your wisdom tooth. Does the tooth have any sharp edges that is pricking/poling your cheek?