When they say tetanus is found in dirt what does it mean? any and all dirt everywhere? in gardens only? in animal feces only? what if you lightly puncture yourself with an earring that fell on a floor and you stepped on that earring with your shoe?

Tetanus bacteria reside normally in the environment, mostly in soil. But the amounts and type of exposure that lead to infection require deep or grossly contaminated wounds: dirty nail that goes an inch into the foot; a grinding injury with lots of dirt (think of a rodeo cowboy falling off a horse, or a shrapnel wound in war). And no risk at all if vaccinated, as you probably were.