hello
1st of all heartiest congratulations for stopping the habbit as chewing tobacco and pan masala may lead to cancer
now by what you describe , it seems that you have developed mild oral sub mucous
fibrosis and those fibrous bands are the cause of thickening of your cheek
also it causes reduced mouth opening
but now since you say that its opening a bit more so u can do following things to get to normal
1.take any antioxidant pill daily for a few months
2.do luke warm saline rinses for 4-6 times daily
3.jaw muscle dialating exercises such as filling your mouth with maximum air and blowing also helps
4.apply placentrx ointment to the affected patchy area
5.if you can ,have a tomato daily as it has
lycopene which is a good antioxidising agent and helps in recovery
best of luck