I have no experience with the booty pillow but if your not applying direct pressure to the area (which is the whole point in not lying on your back) then that may be okay to try. I would definitely ask your surgeon first.
I would need to examine you to tell. If there is still fluid present this can be removed by needle aspiration (sucking the fluid out with a needle). I suspect that you have had some injury to the fat and now have a depressed area that is making the adjacent area look more protruding. If this is...
Arian Mowlavi, MD, FACS (license on probation) says:
You can have any surgery including BBL if you are HIV positive; we treat everyone with universal precautions which means as surgeons we must treat everybody with precautions regardless of HIV status.