I have a recurrent sore in my mouth on the side of my tongue that is sometimes painful. i bit it once on accident, any ideas on what it could be?

Mouth ulcer: Could be anything from local trauma, infection or, if it persists past several days to weeks, it must be seen by either primary care doctor or your dentist. Any lesion on tongue, lips or gums that does not go away must be seen and possibly biopsied to rule out cancer.

Trauma,irritation!: Is that tongue edge near an edge of a fixed or a removable bridge for example? That could be from mechanical trauma , or from infections from a nearby gums or teeth, maintain good oral hygiene and use a mild oral antiseptic rinses, if it persists for more than two weeks , have it examined by a dentist.