Lump in below nipple?

So today (and only today) I noticed this large lump below my nipple in one of my . It doesn't feel like a g or anything squishy, it feels hard. It can't be pushed around, and its caused my to swell a little, also my nipple seems to be pushed inwards. The area is red and itchy, and it hurts to touch. I don't think it could be cancer, because nobody in my family has been diagnosed with it, and I'm only 17. I'm not pregnant, nor have I had a baby, or anything along those lines. Before I go and get my mother all upset though, I just want to have a general idea of what's wrong with me. :( Please help and don't be rude, if you have an immature answer just don't post it.