Allow me to answer your question as best i can based upon your photos. However, please keep in mind that an in-person, or at least a virtual, consultation with physical exam is first necessary before any legitimate evaluation or final surgical recommendations can be made. This is often from a corticosteroid injection, given inadvertently into the buttock fat layer instead of into the muscle. The medicine proceeds to melt away, good fat and even thin out the skin layer creating an indentation such as you have. This tissue is often not a great candidate to accept fat transfer. That being said, one round of fat transfer is usually not enough and if two or three rounds of fat transfer, still do not sufficiently fill in the depression then your only option may be to consider, buttock implants. Buttock implants are definitely a much more reliable and permanent option, as long as you are willing to Increase the volume and projection of both buttock cheeks at the same time. Fillers such as Sculptra and hyaluronic acids are cost prohibitive, provided enough volume is injected (i.e. at least 100 cc of active ingredient costing over $100,000 for something like your case), and last only 12 - 18 months. Additionally, any physician promoting “biostimulators” for buttock enhancement is just a joke, and any board certified plastic surgeon promoting such, should not be trusted with your buttock. Please note that an extremely few number of board certified plastic surgeons specialize in buttock implants, so you may need to travel far and away from home to find this particular surgeon. Getting it done right the first time around is not only the best chance for success, but also will save you from a lot of headaches and money in the future. Glad to help.