As long as it's a wound that can be fully cleaned & washed with soap or antiseptic - and you have done that - it's fine.
The danger is from penetrating wounds, eg. if you get stabbed by things like old screws and nails, where you cannot clean the full depth if the injury.
Also, the tetanus bug lives in soil, especially where animals have been kept - it's basically something like the horse version of a flu-like illness, but with very different symptoms if people are infected.
Things that have been in the ground are the possible hazards - not specifically rusty things.
ps. A proper tetanus vaccination usually needs several shots to have a lasting effect; then another series as a "booster" after ten years or so is supposed to be good for lifetime immunity.
If you have never had the full course, it's worth getting it done regardless.