If you are pregnant, this can have something to do with that. With my second pregnancy, I had a small lump and it had to do with my milk duct. My doctor felt it and said this was the issue and it went away. good luck
Tell your doc and they will most likely have an ultrasound done on your breast. I had one in my second trimester and got an ultrasound. They said it was just a normal change in my breast. Normal mass of tissue. It was nothing to worry about and my great grandmother had breast cancer as well. I'm sure you'll be fine but always better safe than sorry.