Ma'am, Sore nipples happen when the baby doesn't latch on properly. Ensure that when feeding, the baby's mouth is on the areola (the dark area of the breast) and not on the nipple.
You need to let the sores heal. Continue breastfeeding from the other breast and express the milk from the sore one to feed your baby.

1. Clean with cotton wool. kindly see a Paediatrician who will prescribe appropriate medication for the BCG abscess