Hi, mouth ulcers are harmless and they heal on its own in couple of weeks. Do not worry. Usually it develops when you bite your tongue/cheek/lip while eating or due to hard tooth brushing or if you burn your mouth while eating hot food.
Next Steps
Apply gel as adviced. You can try Rexidine-M gel too. Take multivitamin tablets for a week. Do not eat hot and spicy food. Keep yourself hydrated. Have coconut water, curd, chia seeds with water, gargle with warm salt water, do not eat citrus containing foodstuffs.
Health Tips
If it doesn’t heal within 2-3weeks, visit your nearby dentist