The abscess could be a normal one... it is not always CL. However, just to check and make sure, you might want to take him to a vet to check it for you. They can stick a needle in it and if they can draw out normal pus it is probably OK. Then it would need to be lanced and cleaned and he'd have to have a course of antibiotics. If it is CL, what is inside the abscess will be very thick, like cheese. CL stands for Caseous lymphadenitis with "Caseous" meaning "cheese-like". This is a bad disease and if he has it, you want to be certain you don't spread what is inside his abscess around your place because it IS contagious.
As to how to restrain him, I can suggest the head lock on a milking stand, that works well, or the head lock people use for showing Boers or sheep, other than that get a collar on him and use that. Ask for help and try and get several people together to restrain him, if he has horns be really careful no one gets hurt. They can get you good with those horns. Even if you take him to the vet, you will still need to be able to restrain him so you can give the antibiotics. Maybe he will need to be kept in a stall or a small pen that is easier to catch him in, while he is getting his medical treatments.