Is there a filler that can fix a dent after a BBL, or something I can do to soften the hard fat that pokes out? (photos)

Sometimes a dent cannot be corrected to the extent that is desired by PS and patient alike.  There is a certain resistance to change in tissues that can be responsible.  Dents sometimes require release from under the skin.  Fat grafting alone cannot completely fix the issue. Schedule an in-office consultation with an American Board of Plastic Surgery board certified plastic surgeon who has performed these procedures successfully numerous times before and discuss the best treatment plan.
Kenneth Hughes, MD, ABPS Board Certified Plastic Surgeon
Los Angeles, CA

I see a slight  indentation in the first picture which is worse in the second picture. I'm not sure if you've had any procedures in the first picture but that would've been a good place to stop.  Most likely this dent represents connective tissue fibers that limit how much the skin can extend from your gluteal musculature.  It's a form of cellulite.  As the tissues around it expanded this area could not and it now looks in dented. The two options are to cut the connective tissue fibers called substation with small amounts of fat grafting or liposuction in the areas around it or a combination of both. There's a device for Subsicion called Celfina that could help.  Are you happy with the size of your buttocks?  They seem a little excessive to me.  I do not think fillers will work. The amount you would need is prohibitively expensive and because the connective tissue will not let the area expand it won't work.  Best, Mats Hagstrom MD