It looks from the pic that you lost collagen in just that one, somewhat broad, area. It makes me wonder if filler would be a good option for you...perhaps autologous fat transfer, which is basically taking a little fat from somewhere in your body and using it to fill in under the indented area.

There are other options as well, but most importantly is to get under the care of someone really good, because even if you use your own fat, for example, it depends on how good the practitioner is in their skill. You want to make sure it gets more even and not less. Filler can cause issues if done incorrectly. It's also good to get a couple/few opinions from a few derms/plastic surgeons to see what they suggest.