What Does Yellow Build Up In The Centre Of Nipple Indicate?

I have yellow/white buildup in the center of my nipple. It looks like a scab, sort of, and I pluck it out with tweezers, but it hurts afterwards. Normal or...? Please guide me, this is spooky. I m 18 and have never had any nipple discharge, that I know of, and have never been nursing or pregnant.