What Causes A Bump On The Penis?

ive had a hard white bump on my penis on the bottom around the base a little to the left. ive had it for about 3 weeks, i would masterbate alot and i think that may be what caused i so ive stopped. and it seemed to be getting better. until i ended up masterbating and it got hard and seemed to come back stronger. the next day i popped it and cleaned it with peroxide bc i was scared of infection. it seems to be swolled a little but the bump seems gone. the swelling just has me a scared/