Without knowing your set-up, it is hard to tell what may have happened. Keeping him separate is a good idea. Is he the only male in the pen/coop?
If you have a metal feeder, a cockerel or rooster, with long wattles, can get their wattles wet when drinking and then their wattles could be frozen to the cold metal (think the movie "The Christmas Story" and the tongue frozen to the flag pole). When the bird moves, the wattles pull away and can cause injury and bleeding. My males that have gotten frostbite on their combs have never bled. The tips blacken but never have been open wounds. If you can, put some antibiotic ointment on the areas that are damaged.