What Could Nipple Pain With Puss, In Breast Feeding Mothers Suggest?

I am breasfeeding my one month old baby...and I noticed thus pain in my nipple when my baby latches to get fed today only to see a pus formation...I squeezed out. I'm scared now, thinking if my baby has swallowed some of it. wat cud the reaso n be for this and how do I chk if my baby has not had that along with my breast milk?