not saying this is the right thing to do, but i had a similar lump on my ass, swollen and hard, wasnt red, hot , no fever , nothing and i felt fine. just the lump was uncomfortable. showed up like 2-3 days after injection, and also felt like a dull pain like from a hard workout. it stayed the same for like 3 weeks, and i started to get nervous, so i was all over the internet searching abcesses, from what others said, it may have been a hematoma, so i gkept looking into it. well after another week , i saw some really nasty pics of guys that had abcesses cut out of their quads, bi's and delts. NO FUCKIN WAY!!!! they cut the whole chunk out and leave that shit open with gauze in it. and were like that for like 2-3 weeks. i could not explain that kinda shit to friends, family and or work. so i got a 18 gauge pin, iced that swollen area and stuck it in the lump. pulled back on the stopper and started to get this thick redish, pink fluid, blood mixed with some fluid. pulled out like 20-30 cc of it. and it went down for the day. after a few days did the same and again in a few more days. got like a total of like 100cc's all together and it did go away. still have some scar tissue( this was last year.) and a little bruise like mark where the lump was, dont kow what it was ,cellulitis, hematoma , sterile abcess or what , just glad i didnt have to cut cut the fuck open. but it was from the gear i was using, good ol ROCKET FUEL from designer labs. that shit had a lot of BA in it.
18 guage no wonder you have scar tissue. I drained 10 cc's of blood from my delt and used a 21 gauge and it sucked. To get that much out your glute must have looked like hamburger. Must have been hard to reach and see what you were doing as well.