First.............do you know this guy and is he local? If so, take pictures of your injuries and bike and contact the police first to make a report......you need a police report as crazy as it sounds. Then if this guy refuses to pay for all damages then contact a lawyer. I would have my local police make contact with him first to assure him this will not go away!
If all this fails...............sue the hell out of him! I am not sue happy either but a dog like that should not be allowed to roam free due to kids out playing on their bikes. Sounds like a owner that needs a hard financial lesson!
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Ego Campana Inflectum of Circuitous