Would chin filler correct chubby lower cheeks and help me achieve a more flattering side profile? (photos)

Hello, hope you are well. I would not expect or advise that injecting chin filler would reduce the fullness of your lower cheeks. It does increase your chin projection, as does an implant which might be a better option, but that is a separate issue. To reduce the 'chubby cheek' appearance, you might consider buccal fat removal which is a straightforward office procedure that directly addresses the area in question. Consider seeing a facial plastic surgeon who performs this procedure regularly.
Best,Dr. Tower