I have a hard pea-sized lump under my right armpit, it's redder in colouration than the rest of my skin. I noticed it recently (Within the last couple of days) due to it hurting on contact with anything, including my bra. This could have been there longer, as I've never thought to check my pits for lumps, I only check my breasts. I've not spotted any other bumps, but I'm worried. Breast cancer runs in my family and I'm 25.