mate, i am a paramedic and that bump is the base of the hair on your nipple and its got infectid, nothing to worry about, just pull the hair out and give it a squeeze, some puss and gunk should come out, if not , GO SEE A DOCTER EMEDIATLEY, it is possible TO HAVE CANCER ON YOUR NIPPLE, it has happened before , but, NO ONE HAS EVER DIED FROM IT , but it depends on how long it has been there. good luck with it , and dont worry about it!!!