Mak, this sounds like it could be engorgement or maybe mastitis, really important to check with your doctor or lactation consultant soon, especially since you're having pain while feeding and the nipple issue on the left side. In the meantime, a few of us tried warm compresses before feeding and cold compresses after, plus making sure baby latches properly on the right side to avoid more trauma. For the cracked or sore nipples, Mama's Choice Nipple Cream is pregnancy-safe and breastfeeding-safe, and honestly it helped ease the pain between feeds for me. But get it checked lah, because if it's mastitis it needs treatment quickly, don't leave it!