What Causes Lump With Pain In Nipple?

I'm a 17 (almost 18) year old male, recently I've noticed a slight pain and sensitivity to my right nipple, when I rubbed it I discovered that there was a kind of lump underneath it, the whole area underneath the right nipple feels hard and tense compared to my left, I'm a little worried, should I be scared? Too embarrased to approach a doctor and say "RUB MY NIPPLE", please help.