<s>[INST] I had a lump that I initially thought was a bruise from falling over a while ago, that was at the top of my bum crack. And it was very painful to walk and bend over and sleep on my back. This morning it popped an smelt like fart, but the stuff that came out was brown and with some blood. I cleaned it an it seemed to keep coming out with brown stuff, but by the end of the day it was just some blood. I m quite worried as to what this is. [/INST] Hi,It seems that you might be having infection on the part following a fall.there might be having forming abscess and now drained partially.go for one course of antibiotic for 3-5 days.Clean the wound with antiseptic lotion after proper pressing the wound.Apply antibiotic cream locally.If wound is deep, it is advisable to do dressing by your doctor.Ok and take care. </s>