Want to stop breastfeeding my toddler

My toddler has started to bite me a lot. He will bit me once he is done feeding. My nipples are so bruised that he hurts to feed him. I normally feed him when I see him at home after work and when I put him to bed at night. Lately he's been nursing a lot in the night. I don't know how to approach this. When I go home today, hes going to want to feed and I don't know how to say no. But I just can't anymore. He is almost 20 months now.