Gather information from witnesses, if there were any. Get names, addresses, and phone numbers.
Report the matter immediately to the police. This creates a record of the incident.
Obtain the dog's records
Obtain the dog's veterinarian records about shots, diseases and other medical history.
Get homeowners' insurance involved
Do not try to negotiate with the animal's owner privately. Make sure that the claim is directed to their homeowner's insurer. It is best not to engage in conversations about this matter with the owner.
Get an attorney
Talk to an experienced personal injury attorney as soon as possible.