What Does Bump In The Middle Of Breast Mean?

Hi, I was rubbing under my breast last night and under my right breast towrds the middle there is a bump. I just had a mamagram done in January and it cam back ok. It doesn't feel like it is a part of my breast but very close to it. It doesn't hurt to touch and I have also pressed on it and there is no pain. I frequently check my breast and always rub under my breast and I know it wasn;t there last week.