I would give him Benadryl just to help him with the reaction. Cold compresses won't hurt at all. I would not re vaccinate him. Each time he can have a worse reaction. Keep cd antitoxin and tetanus antitoxin on hand in case there is ever a need. I have not vaccinated my herd in many years. I find I have less rumen issues since I stopped. I'm not suggesting vaccinating is wrong, but it's not for everyone. And it's not for this guy.