Does a scrape from a dirty cart require a tetanus shot.?

I scraped the back of my heel on one of those metal granny carts that people push around in the city. More specifically, someone was carrying it and dropped it on my heel. It was bled some, but doesn't appear to be deep. It's very surface level, and I cleanded it well. But because the cart was metal and not exactly clean, I've been debating whether I should get a tetanus shot. I haven't had one in at least 15 years. Is this type of wound at risk?