Toads secrete a nasty tasting mucous through their skin and that is what causes animals who bite them to foam at the mouth.
He probably will not bite another one!
Although....I will say I have one "hunter" who once in a while "forgets" that the little toads in my yard taste bad.
I have lots of toads and most of my pups have at one time or another bitten one with no ill effects.
The bufo toad in Florida is one that is highly poisonous. I don't think you would find one of them in Virginia