since the "after pop" has actually left a bruise of some kind, this would be something to just simply have evaluated by your doc at this point. that would NOT be the 'usual' norm for when any cyst just simply 'pops' and drains itself? the fact you have even had this one cyst there for years? has your doc ever seen it or gave you an indication of the 'whys' as to what formed it and whyi it was just there at all?
have you ever just had an ultrasound done on the whole abdominal just to rule out the possibility of actually having some level of actual 'cystic' type of underlying disease process going on in you? there ARE a few different types of these conditions that one of them i DO have called polycystic kidney disease but it is NOT ONLY within my now very enlarged kidneys? it has taken over both kidneys and my liver and i also have other cysts that have decided to move into other organs and even a muscle in my low back too? people do NOT usually even know thay have this disease til wayy into their late 30s or forties since the labs wont change in anyone til that very real underlying damage just hits that threshhold level and changes start?it actually took my youngest son becomming deathly ill(he was only 12) for us to even KNOW that my side of the family actually ahd this running in it. i found out i had had this crap my whole life, as well as my sister who did not know either, when i was right around 40 years old and with still perfect kidney and liver labs. this IS one insane type of kidney disease, let me tell ya. if you or your doc have no real clue as to why that cyst was even there, you DO seriously need to check out the rest of your abdominal for any other possible cystic growth. i too can feel some of my cysts in only certain places since the organs are sooo freaking huge and i am a very small person? but this just is the most common type of inherited disease process.
if i were you right now, i would definitely seek out your primary to have that area evaled and for him to actually see that "type" of bruising left behind, and to also see about just checking out your entire abdominal with one simple ultrasound too. this cystic crap is very easily seen and actually usually Dxed by US. hopefully that one cyst was a 'nothing', but you just DO need to find that out by ruling out other potential cysts within your body at this point too? esp since this cyst was just even there this long, and what got left behind once it burst and drained too? an actual 'bruise' would simply mean that actual blood vessels were also somehow involved with this too, which needs to be found out as well?
good luck with this and please do see your doc and let me know what you find out, K? FB