I Have Had A Bump On My Leg For Almost

I have had a bump on my leg for almost a year now and it won't go away. Every time I scratch it, it bleeds very badly. When I get cuts everywhere else though they all heal very quickly. What and how do you go about treating this? It appeared a few months after i was told i had mono, does that have anything to do with it? Also is this something i should go to the doctors immediately or is it something that can wait?