I do know that in some places, if you go to a hospital/ER for treatment of a dog bite, they are required to notify animal control and the dog will be impounded.
My aunt's bassett hound bit her hand quite badly while still woozy from anesthetic after surgery...the animal control people were going to impound (and possibly euthanize) the dog, until my uncle and the vet convinced them that the dog was still not in its normal state of mind.
We don't have this ordinance in my area, but I have been bitten by my parents' dog. Actually, it's more of a nip, she's never broken the skin...and she only does it when she's just coming out of a seizure (she's epileptic). Whoever sits with her to keep her safe during the seizure needs to move away a foot or two as she comes out, because she occasionally will nip or growl if someone is too close to her at that time.
If this dog bit out of aggression, your friend needs to curb it immediately, and IMO should pay for your medical bills. Responsible dog owners shouldn't let their dogs be overly aggressive.