Since he's reopened the wound several times, I am hoping it's not
infected. Is he friendly enough to let you pick him up and examine the
ear? Is it red, inflamed, pussing? If it's infected, he'll need to be
seen by a vet for treatment.

If it's truly just a cut/scrape, you can put a tiny amount of
neosporin on it and rub in. He can't lick his ear to ingest it.