Hello sir... the difficulty in opening mouth isdue to tobacco chewing only...you need to visit dentist for furthur management....treatment depends on degree of mouth opening you are having.... the treatment varies from topical steroids, intralesional steriodal injection depends on degree of mouth opening you are having

Just taking a Medicine may not cure it if it works well n good Best would be you can opt Injection threapy from Oral and Maxillofacial Surgeon If dosent work you can go for Surgery Followed by Reconstruction

Visit an oral and maxilofacial surgeon... After proper diagnosis he will guide you..

First you have completely left tabacco. mainten  good oral hygiene. Some excreise you have done for increase mouth exercise ex icecream spoon . Start medicine of anti oxide for lysis of collgen fibers. Ex lycopin

If the diagnosis is confirmed start taking capsule SM Fibro, twice a day for one month, and do visit a dentist soon for follow up