Based on the information provided, it looks like a case of apthous ulcer. These have no known cause but can be a symptom of
vitamin deficiency or a tooth which is rubbing against the inside of the cheek.
Next Steps
Start tablet BECOSULES once a day after meals for a month.
Visit a dentist to rule out any tooth issues.
If you have recurrent ulcers anywhere else om your body in addition to the mouth ulcers visit a rheumatology specialist.
maintain proper mouth hygiene.