What will happen if there's small amount of tetanus on the food you ate?

Nothing, even if you are not vaccinated. The bacteria responsible for tetanus is present in stomachs of cows and horses, and they live very well with it. It needs a deep wound to contaminate somebody.

Why don't you check WebMD? It might have some answers for you.

Tetanus is a bacterie and probably nothing will happen if it's (just a bit) in your food. Also it's not said you will get tetanus if you stand into a rusty nail. The bacterie is all around us (if it comes to that) so big chance you already been in contact with it (and have antibodies). It's proved that the more "clean" or hygenic we are the easier we get (seriously) sick. I never had tetanus, never had a shot against it either but I can assure you I have had plenty of injurences (very bad ones incl. infections) and bad food to get tetanus. I might have had it but recovered myself (although I have a bad health, many allergies and auto immune diseases). If you feel fine, don't talk yourself into any sickness. You get way more (bad) bacteries) in your body as you can even imagine (not to forget the poop-bacterie in restaurants, etc).