The wound may simply have been an abscess from a puncture as simple as a splinter of wood -- they're rubbing on stuff. Those will be a fast moving build up of simple pus, a bodies reaction to damage. He could have picked up chiggers from trees. Iodine. Then Vaseline on ear spots. Have any paste dewormer? Rub a touch of that on the ear patches. It'll kill mites, lice, etc. good for the goat.
This treatment can save a vet call. Watch for improvements. Also, original gold Listerine is good for fungals, hotspots, etc. I've used on horses, cats, dogs. It clears and heals. Itch stops & inexpensive.
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