Hii,
It may be due to several reasons. Few coomon reasons are use of tobacco,pan masala, betelnut chewing, smoking, deficiency of certain vitamins, apthous ulcers.
If u are having any habit, it is advised to quit the habit. Drink lot of water make urself stress free. Take antioxidant rich diet and medicines such as SM-FIBRO or LYCOSTAR twice daily for 10 days. Apply kenacort oral gel upon affected area. If symptoms do not start subsiding within 2-3 days, it is advised to take appointment with a dental surgeon.
Next Steps
Appointment to a dental surgeon