What to do with sores on the tongue? Its painful when I eat on the sides of the tongue

Aphthous ulcer? Aphthous ulcers are quite common and most adult experience it at some point. It is often small of around 1/3 in in size, whitish base with red rim. Despite small, it can be quite painful. The exact cause if not known, but believe to have some autoimmune components. Otc sorethroat spray, motrin/aleve may help. Steroid rinse/paste may help. Herpes ulcer causes some pain too. Consult doc ..Good luck.
See your doctor. He may prescribe ointment or paste to help. He may recommend a biopsy be performed usually in the office. There are common causes which are not harmful and there are some causes which can lead to cancer.