Mouth not opening. There any medecine.

Going by the description that you have mentioned it seems that you are suffering from Oral Submucous Fibrosis. You seem educated enough to understand that your tobacco usage is the cause of this problem. So the first thing that needs to be done is quitting this habit immediately so that the symptoms do not aggravate further. You need to visit an oral pathologist or an oral medicine specialist for a proper diagnosis and determining the stage of your Oral Submucous Fibrosis. There are various treatment options with varying success results for Oral Submucous Fibrosis ..... the best treatment option can be explained to you after a proper diagnosis has been made. Medicines like antioxidants can help in improving the healing slightly but they are not the cure for this problem. Regards.