Poor guy. Do you have banamine? Or dexamethsone? These can help with inflammation and pain. Keeping the hoof clean and dry is most important. There is a product called Kopertox that is good for hoof rot. Not sure what your area of the world carries. But maybe look it up and see what might be available locally. If not keep with the biomycin a few times a day.. Keeping him penned in a dry lot with food and water close will help. Don't want that to spread to other goats.
Best wishes
Best wishes