Tetanus is caused by a toxin produced by bacterium. It exists in soil and animal feces. Cutting yourself on rusty steel or iron would be concerning if it was in the ground for some period of time. Regular wounds won't have Clostridium Tetani in it. The dogma of getting a tetanus shot whenever you are cut has become ritualistic. Another scenario where better safe than sorry has gotten over played and the fact that doctor's don't know the mechanism for being infected with Clostridium Tetani is very concerning. If the doctor had the information of what you are cut with and the location and circumstances of the wound, they would know they you had virtually no risk, that would not justify the hard sell on getting a Tetanus booster