Hi.. Thanks for writing to us.. I have gone through your query and can understand your concerns.. As per your query and presentation of symptoms of locking of jaw or reduced mouth opening with a history of chain smoking and tobacco chewing can be due to most common reason that is Oral Submucous Fibrosis in which there is formation of thick fibrous bands below the mucosa of cheeks and lips leading to stiffening and difficulty in mouth opening.. It is a precancerous condition [although not cancer] and should be taken care of. It is commonly seen in individuals with tobacco and areca nut chewing habit.. It will not resolve on its own even if after it occurs you stop tobacco chewing habit and needs proper management for improving mouth opening.. You need to consult an Oral Physician or a Dentist and get evaluated and he can advise him to apply a steroid ointment in combination with hyluronidase containing ointment to break fibres.. Intra lesional injections of steroid and hyluronidase can be advised to be injected after every 3 to 4 days.. Anti-oxident like Lycopene is also advised.. Physiotherapy like blowing cheeks, trying to open the mouth under pressure etc can be demonstrated and advise to be done daily.. Complete cessation of habit of tobacco if you have chewing is must .. Hope this information helps.. Thanks and regards.