I just went through this. My rooster hid in the coop for the first few days after the attack. His comb was laying flat on the side of his head like a leghorn hens comb.
He slowly started coming out of the coop. He still didn't act right. He didn't mount the hens, didn't crow, wouldn't come and take treats out of my hands. After about a week, he started coming to get treats, but still didn't do the normal roo things. His crop started to swell.
I was pretty sure I was going to loose him. I just kept babing him and leaving him in his comfort zone. Finally, about a month after the attack, his confidence was back. he started crowing and mounting hen.
Make sure your boy has food and water. He may have internal injuries from the attack, but he may just be sore. His confidence may of been at an all time low.
What we had to do with our dog was use a shock collar. We took him near the chickens on a leash and when he even looked at them, he got a little shock. This worked like a charm. He stays away from them now, yet still acts as a guard dog against chicken predators.