When cut by rusty metal, do you need a tetanus shot?

Q. If you step on a nail and have not had a tetanus shot in the last five years, how soon should a person be vaccinated?
A. While tetanus is a serious bacterial disease, there are many factors to consider and symptoms to look for when determining whether or not you need a vaccination. Health professionals recommend that adults receive tetanus boosters at least every ten years, as preventing tetanus is much easier than curing it once infected. If you step on a nail and haven't had a tetanus booster in the last five years, visiting your health care provider to get it checked out is recommended. It’s best to seek treatment sooner rather than later (preferably within 48 hours) to increase your chances of treatment if, in fact, you're infected. Even if you’re still concerned, despite knowing the date of your last tetanus shot, having your medical provider take a look may provide some peace of mind.  
It isn’t the rust that causes the infection, rather it’s a type of bacteria, Clostridium tetani, that's on the rusty nail that causes the infection. This bacterium is ubiquitous in the natural environment — spores lurk in soil, dust, and in animal intestines and feces. The rusty nail scenario isn't the only way this disease spreads. Any deep puncture can become infected with Clostridium tetani.
The bacterium may produce a toxin that interferes with the central nervous system, producing muscle stiffness, rigidity, or spasms. The most frequent symptom is a stiff jaw, followed by a stiff neck, and then muscular stiffness and spasms throughout the body. Other symptoms include difficulty swallowing, restlessness and irritability, fever, headache, and sore throat. More serious complications include broken bones (due to involuntary spasms), pneumonia, difficulty breathing, cardiac arrest, and death.
Tetanus symptoms appear anywhere from a few days to several weeks after the tetanus bacteria enters the body. Currently, laboratory tests are unable to diagnose tetanus. For those certain their vaccinations are up to date and if the puncture is small, it may be safe to just clean the wound, treat it with antibiotic ointment, keep it covered and clean, and be on the lookout for symptoms.
Source: Columbia University health professionals: goaskalice.columbia.edu