Chewing your cheeks could definitely damage them. Some people believe that long term chronic irritation can cause cancer, and it's a possibility that the issue is exacerbated by smoking, that said its probably not, but if you've had it for more than three weeks, and it's unhealing or getting worse then it's best to have it checked out but someone who knows oral cancer, ENT, dentist, oral surgeon. Bottom line I'd quit smoking regardless... Good luck!