Hi and welcome to HCM!
Thanks for posting your query here.
Gutka chewing, swelling in the right cheek, not able to open the mouth gives a clue to oral cancer
The contents in the gutka are the most potent carcinogenics. This causes mucosal fibrosis
which will cause difficulty in opening of the mouth. It presents from a simple ulcer to a benign lesion. This can be confirmed only by the biopsy
The treatment depends on the staging of the lesion, your fathers health status- diabetic, hypertensive, and on immune system also. In most of the cases it is curable to an extent of 90%.
Please wait for the biopsy report. If it is a simple ulcer it can be cured within a span of 1 month. Give him light and easily swallowing foods-like semisolid foods. Please ask your father not to have gutka anymore. Take care of him because since 10 years they are addicted to that.
Hope this clears your doubts.