Hello Doctor. I Recently Went To A Dentist And Reslised

Hello doctor. I recently went to a dentist and reslised that I can partially open my mouth (gap of 2 fingers) the dentist said that it is because of smoking and that It may lead to cancer. Its been over a week and I have left smoking now. He gave me capsules to take 2 times a day for 15 days. I also do stretching exercises few times a day. Though I am still unable to see even the slightest of the changes. Any suggestions or help?

Thank you.