As mentioned by others, if you bleed you have no risk of contracting clostridium tetani, which is the bacteria that causes tetanus. It comes from animal manure, so if your car wasn't pulled out of some old farmers field recently, there is nothing to worry about.
The old "step on a rusty nail" thinking is a myth.
And here's what they won't tell you, getting a tetanus shot AFTER you are in contact with the bacteria does nothing. It will protect you from a future accident, but not the puncture you are dealing with in that moment.
