More than likely they waited too long and the infection formed a hard case around itself (abcess), making it dangerous to just drain because it could burst and release the infection into the bloodstream causing multiple complications even death. If you were to get an infection and you noticed symptoms right away, most can be taken care of by antibiotics or drained. Unless there is a foriegn object in the muscle that was in the oil or on the needle (hair, dust, piece of cotton swab) then it may be necessary to cut you open. BE CAREFUL BROS, and if you feel like your getting an infection, take some antibiotics right away and/or go see the doc, you don't want to get a chunk of muscle cut out because of stubborness!! The shit doesn't just go away!