No, it's not a good assumption. You don't mention where you live. Generally speaking here on the west coast we don't see rabies in squirrels. I think there may be a few cases out east but it's not common. The most common rabies vectors are foxes, skunks and bats. Theoretically, any mammal can get rabies but that doesn't mean every mammal species does get rabies.
Because the bite is a deep puncture wound (and squirrels don't brush their teeth) you should go see your doctor to have the wound properly flushed out. It will be up to them whether you should go on a course of antibiotics.
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