The type of injury that you had is the very type that is high risk for obtaining an infection with the bacteria that causes tetanus, so I recommend that you speak with your doctor
. Tetanus is caused by the bacterium clostridium tetani. This bacteria loves to live in the dirt and on rusty metal such as what you stepped on. While certainly cleaning the wound and using Neosporin will help prevent some infections, it will not likely prevent infection with tetanus. This is the reason why being vaccinated is so important. A tetanus shot is supposed to last about 10 years, though during the last five years there is usually some waining of immunity. This is why we always recommend that somebody get a booster tetanus shot if they have such an injury after five years have gone by since their last shot. Since it has been seven years since your last shot, most doctors
would recommend that you obtain a booster tetanus shot within a few days after your injury. I would suggest that you schedule an appointment with your primary care physician
to further discuss this issue. I think that most likely your doctor will end up wanting to treat you with an additional tetanus shot at this time to help prevent infection. Good luck.