Corid is for coccidiosis, so I wouldn't be giving it to the injured chick. Keep her warm, quiet and isolated from the other chickens so you can observe her. If she was pecked in the head and/or neck, she may show signs of neurological damage, such as poor balance, inability to walk or stand properly, inability to hold her head upright, inability to eat or drink, etc. If these symptoms persist for more than a few days, you may have to consider putting her down. If you're not seeing any of these signs, she may just need time to heal from the injury.