Jaw pains only on the left side, what could be wrong?

Number of things: Jaw pain can be related to a dental or tooth related problem, a TMJ problem, a soft tissue problem in the cheek or face, a salivary gland problem, as well as a problem within the bony structures of the upper and/or lower jaw or associated facial bones. Without more specific information, the best recommendation for you would be to see either your dentist or primary care physician for evaluation.