u must have bitten on cheek...visit nearby dentist for evaluation

Your problem is very commom.as you correctly said you might be biting cheek during sleep or as you are 19 there could be possibility of you getting a wisdom tooth .

First of all you need a proper evaluation of your dentition to ascertain whether the reason for regular cheek biting is psychological or physical or both. The physical reasons can be malocclusion of the teeth wherein their positions are such that they make the soft tissues more prone for injury, or it could be lack of tonicity in the cheek muscles because of which they are continuously drawn between the teeth while chewing. The psychological evaluation will be done based on a series of questions which would be asked by the dentist who performs the physical examination first. The treatment will also depend upon the diagnosis of the physical or the psychological component. Although it is difficult to immediately rectify the psychological component but efforts can still be made for that. As far as the physical factors are concerned, oral appliance called as oral screen can be fabricated for you which can prevent this habit. At the same time some exercises can be suggested to you so that the tonicity of the cheek muscles can be improved like holding the water in your mouth or holding the air in your mouth for a minute or so and repeating this exercise multiple times in a day. Regards.