Dear sir
First of all I would like to know if there is any ulcer(wound) or swelling in that area which is visible to your eyes. Also do tell me if you have any decayed teeth on the affected site
Most commonly this kind of problem exists in patient who has a decayed teeth which has infected the bone below
Or from the habit history
It can be a serious problem if it is some kind of cancerous condition
Next Steps
Please try and avoid the tobacco chewing habit.
Health Tips
Consult with a dental examiner as soon as possible
Because he can examine it visually and if required with x rays
And come to a conclusion of your problem and advise accordingly