I have a white painfull blister in the inner wall of my mouth. what could it be and how can i treat it?

More info: Most blisters in the mouth are viral. Some painful. Some not. You can get lesions your inner cheek from a chronic injury (bite) from your teeth. If the blisters/sores make it painful or difficult to eat or swallow, then you need to see your doc. For an rx. You can sooth your mouth by combining equal amounts of liquid benedryl, maalox and oral analgesic. Swish around and spit it out.

Canker sore : This sounds like a canker sore (aphthous ulcer). Topical medications like zilactin or anbesol may help. If it doesn't go away in two weeks, you should have a doctor look at it.