Weight Gain to Correct Sunken Cheeks?

You could try healthy weight gain and see if that works first. If it doesn't fillers can help add some volume here.

There is no surgery that can correct sunken cheeks in that location since that is just to the side of the mouth and is really just cheek skin. Gaining weight would be advisable.

Hello Hefty,
I agree with Dr. Lentz that fat grafting is an excellent consideration. I would also add that given your age and that you look "skinny if anything", then you should consider putting on some weight in a controlled and healthy manner. In most people your age weight gain is easily reflected in the face. Putting on some pounds may be all you need, if not then you can certainly consider the opt ion of fat injections / fillers.
Take Care,
Dr. Kamran Jafri