Difficulty in mouth opening in a person who cgews tobacco is due to Submucus fibrosis. It needs to be evaluated by a oral surgeon. It is a pre cancerous condition. So, please see a Oral surgeon as soon as possible. Also, it is important for you to quit tobacco chewing. please see a psychiatrist to prescribe you nicotine replacement in the in the form of nicotine patches or chewing gum. Also you will need anti craving medication to overcome craving and withdrawal symptoms. But on priority please see oral surgeon as soon as possible.