Ok I'm 28 Yo Fm.. My Nipple Was Swollen N

Ok I'm 28 yo fm.. my nipple was swollen N tender N hard. Areola is normal.. my baby is 18 months old.stopped breast feeding when he was a month old. I still lactate. Seeing no infected area ipinched the nipple N a small spot came open and a hard white core I'm thinking dried milk came out.. then a good amount of puss N a tiny bit of blood. I'm curious to know y this happened?