feeding, blood blister on nipple HELP?

I've been feeding for 6 months. My left nipple has been hurting when he eats, but I continued to feed him anyway. Last night I was feeding him and it was unbearably painful and I looked and there are 2 black blood blisters. Through the night he fed from the right and I thought I'd pump from the left this morning. It is very hard and full of milk, but not much is coming out as fast as it normally does. Could the blisters be blocking the ducts?