You’ll need antibiotics but you really should call the Vet to get the best scrip for the most common bacteria. You can administer the shot yourself. Our large animal vet will listen to me on the phone and give me his best diagnosis based upon what I’m telling him if I can’t afford to bring the calf up there. Get the calf’s temp. rectally, monitor his breathing, Breaths per minute. I might give him some penicillin for tonight, since it’s after hours with the vet.. You may be able to get it at tractor supply. Calculate based upon his weight.
Soak the navel in warm salt water, see if you can squeeze uout the infection. Pat dry and swab it down with iodine.
Don’t wait. Once it gets to his joints that can be pretty bad.