Bubble inside mouth after being hit hi, I was hit two weeks ago on the cheek with an object, specifically a badminton shuttlecock, at high velocity and a couple days afterwards, a bubble developed underneath the gum-line of the bottom set of my teeth. It

The . The gum tissue surrounds all of the teeth in the mouth and contains many blood vessels. It sounds like the object may have ruptured some of these blood vessels and the result is a deep bruise filled with blood, causing the gum to bulge. A more serious situation is a fractured tooth root which became infected and caused an abscess. My advice is for you to go to your dentist or a specialist such as a periodontist or oral surgeon as soon as possible and seek out appropriate treatment.
This . This looks like a tooth that has a nerve that has been severely damaged by the blow. It should be treated immediately. This advice is of course based only on your history and the phot which does not substitute for an examination by a competent dentist.