Green/yellow lump in my right breast?

Holly • Don't let anything stop you

I'm 15 and for about a couple years I have had a greeny yellow lump in my right nipple. It's got a bit of blackish brown in the middle of it and also a black lump a couple mm down. I'm very concerned as as well as reducing my self esteem, it is also making me worry thinking I might have cancer. The other one is fine, it's just the right. I do however wear bras when I'm sleeping because...

Thanks.