Or could it wait till tomorrow?
Don't worry, based on what I see he'll be okay till tomorrow.
See the sort of ring or circle shapes in it? That is a very common growth pattern of fungus. Fur mites usually leave a much more ragged edge.
I have no issues whatever with using chemicals on my rabbits, so I use some things that are much more harsh in nature than many people here. For fur mites I have used Sevin (a garden insecticide powder) sprinkled on like flea powder, for ear mites I have used bird mite spray that you can get at Walmart- I soak a cotton ball and then swipe it down the inside of the ears. I have also used Advantage flea drops dosed at the cat rate- it works excellent, but is very expensive. If you head up to Marysville, I know you can get Advantage at Jones and Co Pets, and at Co-op Supply feed store.
None of my rabbits has ever had a bad reaction to these things; also, I don't eat them so that's not an issue for me.
I've not had fungus in my rabbits, but my dog has had fungus several times. Don't know where she keeps picking it up. Always in summer, too. For her I use clotrimazole cream from Walmart, for athlete's foot. Takes four or five days, clears it right up, and then it's gone... until next summer. Just smear it over the affected area and a little over the edges into the healthy area, one or two times a day until the skin is cleared up.
Hope this helps!
And don't be down on yourself, seriously everyone gets things like this once in a while. One day they're fine, the next day you go out there and everyone is scratching their ears, or whatever. That's just part of keeping animals- :farmer2: :dogkiss: