As you know, skin wounds caused by rusty metal can put you at risk for some unpleasant infections, including tetanus. The bacteria that cause tetanus do not grow well in the presence of air, so the most common types of injuries that can cause tetanus are deep puncture wounds (ie stepping on a rusty nail) where the bacteria are embedded deeply into tissue away from the oxygen at the surface. However, anytime you have a cut of any kind that was caused by metal, especially when you know it was rusty metal, you should be evaluated by a physician. Even if the wound is not high risk for tetanus, there are many other bacteria that cause cellulitis or skin infections. Hopefully the wound is not so serious you will need a course of antibiotics or stitches, but the best thing to do is see your primary care physician
immediately (or through an urgent care center) for wound evaluation. You will definitely need a tetanus shot just in case (and you need one every 8 years anyway), and your physician can also evaluate whether any additional wound care
or antibiotics are needed. If you can't see your own regular physician right away, you should go to an emergency department for evaluation since wounds caused by rusty metal should be evaluated promptly (and for tetanus shot administration).