My son's face has sunk in a bit on one side and I was wondering what could be done to make it look the same on both sides?

Thank you for your question.  I would recommend visiting with a plastic surgeon who sees children/teenagers to discuss your options with you in more detail.  Procedures like dermal fillers or fat grafting are great ways to bring about more symmetry in the face.  But I would only proceed if it is affecting your child psychologically or impacting school.  If it is only a minor concern to him, then I would wait until he grows older into adulthood.

Voluma is an excellent alternative to currently used fillers. We use it for restoring mid face volume in the cheek that had previously been difficult to enhance. We have seen great results lasting 12 months and more. I would suggest you discuss your concern regarding your prior treatment with a dermatologist that has experience with Voluma. 

Without photos it is very difficult to make a diagnosis and thus difficult to advise for a treatment. One thing comes to my mind though from your description and it is called Rhomberg syndrome. If this is the case, it can be of several degrees and treatment differs with the intensity and ranges from fat filling to more complex procedures. best, Shady Hayek, M.D. Plastic and Reconstructive Surgery Beirut, Lebanon 

Everyone's face is asymmetrical.  If there is significant asymmetry for your son, please first see his pediatrician to make sure he is progressing appropriately developmentally.  His face will continue to change throughout puberty.  For most adults and young adults, hyaluronic acid (HA) fillers can help improve facial asymmetry when place appropriately.  These HA fillers include Voluma, Volift, Restylane Lyft, Restylane, and Juvederm Ultra Plus for the cheeks.  For adults, your dermatologist or plastic surgeon may also consider Sculptra. Best,Suneel Chilukuri, M.D.