@Brian430
No matter how well trained a dog is they do have a mind of their own and once this happens once there is no way you can guarantee that it won't happen again.
As I see it you have two options....
A/.......Relocate the dog somewhere else so there is no possiblity of contact with unfamiliar people!
B/.......Stop hosting and having strangers in what is the dogs space!
Airbnb will not cover you in this instance because they will consider you did not take adequate measures to protect the guest while they were on your property....this is not an accident, it is a potential foreseen event. In many parts of the world authorities will remove and destroy dogs when they bite somebody!
I feel for you terribly Brian, we are the owners of a dog and I know how attached you become to your pets. We would be devistated if this ever happened to us and we were forced to give up our Betts! Fortunately our dog has an extremely placid nature and loves people...full stop because to her people mean pats and treats.
If you feel you need to keep persisting with having this hound and guests, I would suggest that you keep a bag of treats at hand and as each guest arrives get them to feed the dog a treat so the dog learns to understand that strangers mean something good is going to happen. A friend of mine did that and it worked, although his dog never bit anyone but, would growl when strangers came into its space. The dog now accepts strangers with the wag of the tail and waits for its treat!
In this instance Brian, refund the guest and get a professional opinion on the nature of the wound, don't think that because it doesn't look much, it must be ok. We know a woman who lost a finger due to complications from the **bleep** of a rose thorn....it didn't look much, in fact you could not see it but...she lost her finger!
Sorry Brian not a nice thing to have happen and I hope you get out of this without too much pain!
Cheers.....Rob