Thank you for this excellent question. Two months after a BBL, your butt is hard because of swelling and inflammation. Dr. Andy Kaczynski, of Sacramento, refers to this early post fat injection firmness as pre-scar. This is very common after both liposuction and fat injection, and can be treated with a combination of DMSO and ultrasound (the kind physical therapists use for sore muscles). The DMSO is compounded by a pharmacist and is a special formula which your plastic surgeon either knows or can easily find out. Please do not try DMSO that is not prescribed to you by your plastic surgeon. DMSO is the world's best anti-inflammatory. It takes down inflammation in joints and in soft tissue. It also brings blood supply to an area which helps carry away the breakdown products from fat injections or from liposuction. DMSO opens up choke vessels, a redundant blood supply we all have all over our body, increasing the body's ability to get rid of bruising and, what you are referring to, as hardness. With reference to the hard fat your plastic surgeon refers to, this very often means that your fat is held in more fibrous tissue, and therefore is more difficult to suction out. This tissue can also be softened by putting DMSO on the area to be suctioned, 4 times per day for 4 days prior to the liposuction. Ultrasound is a means of sending in sound waves from a machine often used by physical therapists. The sound waves are converted to heat which increases the blood supply to an area, therefore increasing the body's ability to carry away breakdown products of fat grafting. Also the sound waves tend to break up clumps of fat allowing more fat cells' survival (a bigger butt), and since you are decreasing the amount of cells that have to be carried away, you are decreasing the inflammatory process which makes your butt hard.Above are two useful post-operative, non-surgical techniques that I have used at the Mommy Makeover Institute of Hawaii for over 20 years.