Hi I Had A Surgery For A Biopsy For Possible

Hi I had a surgery for a biopsy for possible breast cancer. It was behind my right nipple. The surgeon cut half around my nipple. After a couple of weeks my breast started to get red on the skin itself and I have like puss sacks under skin and have pain. I was given 500 mg capsules of Cephalexin to take twice a day. 20 of them. I can still feel puss sacs behind skin and it still hurts. Do I need to worry about staff infection or worse with this?