Thank you for your query at DoctorSpring.com
I understand your concern.
This is a canker sore, or what is commonly known as an apthous ulcer. I can understand it is very painful and cause a lot of discomfort while eating, brushing, chewing ( e.t.c ). However the good thing is it happens to a lot of people and if not persistent, then there is no reason to worry. I will advise you an ointment and once you apply that directly on the ulcer, it will get better. It is common in diabetics, as they are more prone for infections. Can also happen as a result of vitamin deficiency, or eating extremely spicy food which acts as a local irritant.
Please take the following medicines :
1) Xytee gel ( Metronidazole gel ) ointment apply 3-4 times daily till there is complete recovery.
2) Tab. Zincovit once daily at bed time for a month.
3) Try to avoid chewing from the affected side. Also avoid too hot or spicy food for the next 2-3 days.
Hope this was helpful,