Yesterday I noticed a pain in one of my nipples. It's sore, and I had to actually roll over to lay on my other side so it wasn't touching the bed when I slept. There's a lump under it. Not under it visibly, but I felt I guess "behind" the nipple and there was a lump there that wasn't behind my left one (behind as in, inside the breast). It's sore even when I'm not touching anything. I'm only 17, my grandmother's had cancer, my mother's had cancer removed, I'm scared. Unfortunately I also hate needles. The lump itself (forgive the comparison) feels somewhat like a pimple, or the thing inside the pimple when you can feel it and try to pop it, except much larger and more painful.
What could this be? Should I be worried?