Tetanus, also called lockjaw, is very rare in the United States because most children are vaccinated against it. Tetanus is caused by a bacterium that is common in the soil, but dies quickly when it is exposed to oxygen. People who haven't been vaccinated for tetanus can get the disease by stepping on a dirty nail or getting cut by a dirty tool. The bacterium produces a toxin, or poison, that spreads in the bloodstream and can result in severe muscle spasms, paralysis, and death.
Tetanus is difficult to treat, but proper vaccination prevents it. Children get a tetanus shot in combination with pertussis and diphtheria vaccines. Adults need a booster shot every ten years to make sure they are protected.
If you have an open cut, you should figure out when you had your last tetanus booster. If it is more than 10 years ago, it's time to get vaccinated again.