I need more details of your problem. You have to tell me since how long you are having the problem and also which molar you are having problem. I also need to know whether its a blister
or a swelling. However with the symptoms what you have mentioned, it looks like you are having either pericoronitis
(if at all if the swelling/blister is arising from third molar/wisdom tooth ) or periodontits, which would have resulted in abscess formation. Both pericoronal abscess
and periodontal / gingival abscess
will not have much changes in radiograph (xray). If in case it is an abscess, drainage
of abscess has to be done. If it is due to wisdom tooth and the position of wisdom tooth is unfavourable then the wisdom tooth has to be extracted.
Having suggested this I request you to elaborate your problem a little more so that proper answer can be given.
Wish you a speedy recovery