Just as an aside. Sometimes humans get open sores from a grit of soil getting in an open scratch. They can develop to tropical ulcers. My cat had a large lump from a tic-bite that had a small outer sore.
I had Gano Excel Detox capsules. This detox coffee contains ganoderma lucidium miscellium which is a rainforest mushroom from the canopy containing over 200active ingredients. Reishi mushroom aside. I have opened a capsule and sprinkled about one third of cap on the cat's wet-meat (about 1oz x3/day). I sprinkled some Gano powder directly on the sore and in her feed. So far my friends and I have experienced satisfactory results with using a touch of Gano on sore and food, for sores on horses, dogs, cats, goats and humans. With humans it can work tremendously fast with a direct exterior application but best with a detox course. With the horse I'm told it worked in a few days. As too with the goats. With the Ed dogs and cats it is much more difficult to keep checking the cleanliness of the sore but usually the interior and exterior application will clean up a sore in three days. The vet will want you to keep spending OR will be interested to know, depending on his finances and dedication to learning. This we learned by applying when no vet available.