When i run i have a pain under the tongue.

Slow down & destress: A pain under the tongue could be that you are over stressing . Watch your breathing technique . Try some yogic breathing. If the tongue is forced between the teeth while you are clenching, and trying to breathe, it could be a source of tongue pain. Open the mouth about half-way, look at the sides, if you see scallops in the lateral borders, you are definitely clenching, [maybe at night also. ].

Salvary/ muscle: Without the benefit of an exam or xrays it is impossible to diagnose your problem. I would advise you to see an oral surgeon and be prepared to answer some question.. Do you have the pain only while running. Do you have a similar pain when getting ready to eat. Do you clench your jaw while running. Do you wear a mouthguard. You need to determine if your problem is glandular or muscular in nature.