Got teeth marks on either side of tongue what causes this?

Clenching is likely: Chances are you are horribly hungry and need to find something to chew besides your tongue or you have a teeth clenching issue. This is typically accomplished in your subconscious while you sleep and you pull suction in your mouth and squeeze your teeth together. The tongue gets that pie-crust appearance on the sides. This is all simply speculation so have a qualified dentist diagnose for sure.

Often : This can be seen in people with larger than average size tongue or if the tongue width is wide or their teeth arch is constricted (narrow) or they clench& grind their teeth. Some people chew on their tongue while doing other activities.