Seems like a bite due to a sharp tooth edge. If doesn't resolve over a week's time visit a dentist. For pain relief you can apply an aneasthetic gel over the affected area specially before eating

Hello, if the lesion that you’re referring to is irritating and burning while you touch it or eat something then high chances are that it will go away. However, I’ll need more information on the same to give you a definite diagnosis that whether this happens regularly or it’s the first time? Are you under some sort of stress?

Mostly its ulcer

Hi, Please visit a dentist and get a clinical evaluation done. Check for any sharp tooth edges. There is nothing to worry. It will go away in a day or two.