Possible sebaceous cyst on scrotum - is it infected? I noticed a large swelling / bump on the top of my scrotum, where the shaft of the penis meets. Rather foolishly, I thought it was a very large oily pimple and tried to pop it. It didn't go away. For the last few days, I applied a warm compress and washed it daily with Dove soap. This morning, the swelling had gone down a lot (almost none), but there was an open tiny black 'hole' with a liquid similar to pus oozing out.