Might have Breast Cancer...?

I don't know if I do or don't because there is a lump right under my right nipple that has an indent at the top. But, i looked online and it says that everybody gets this while going through puberty, and i am 13. I have been developing arm muscles, body odors, and pimples and stuff like that, but i noticed my hair has been coming out slightly... although this could be because I have an afro and pick it every now and then. My dad also told me just recently that my grandmother has breast cancer and she has to take a test to see if it is genetic. If it is genetic, they have to see if my dad has passed it onto me and my siblings. I am just not sure and need an answer just so i can relax. Thanks for the help.