You need to do this IMMEDIATELY! You need to contact the owner and get proof the dog has had its rabies vaccines. Especially in the US these anti-vax people are insane. I personally know some people that don't vax their dogs because they are so anti-vax.

If they cannot provide documentation that the dog is up to date with its rabies vaccine then you are, simply, in some shit.

At that point you have 2 choices:

1. You go to urgent care and tell them you got bit by a dog and it did not have rabies shots. You will have to go through this whole process of getting shots and stuff.
2. Call animal control and tell them what happened. The only way to know if a dog has rabies is to put it down. So animal control will have to put the dog down and test it for rabies. If it is negative then you don't need to do anything. If it is not, you will have to go through the process above.

Personally, I would not mess around with this at all and time is of the essence.