I had that happen. You have choices. You can lock the cockerel up until his hormones calm down. Hopefully he would then turn into a wonderful rooster. I rehomed mine. He took a dislike to my very favorite hen. I'd separate her and get her healed up. As soon as he saw her again he'd be after her. He was fine with the other 10 girls. My hen was the alpha hen of the coop. I think she fought the young cockerel's breeding attempts. That is why he decided to always beat her up. A rooster will grab hold of the back of the hen's neck when he breeds and that is where the damage was done.
