How to fix an uneven jaw without surgery? (Photo)

The picture is not really adequate to give a proper answer, but I think that an injectible filler may be able to give the results you are looking for.  There are several types of filler that can be used.  Seek the advice of a board certified oral and maxillofacial surgeon to help with your concerns

A more defined jaw line can be achieved after a proper consultation and assessment of the facial skeleton, overlying muscles, and thickness of the skin. All three aspects of the anatomy will dictate whether orthognathic surgery is warranted, usually in a skeletal dental abnormality, or whether the masseter muscles are enlarged. Also, the buccal fat pad may play a role. 

This may just be a difference in muscle attachment from one side to the other.  In this case, I would recommend an injectable filler. If there is a true lower jaw asymmetry, then perhaps further radiographs and work up is required.  In this case, surgery may be your only option to correct the condition.Best of Luck!