It can also be short for "putting your foot in your mouth," as in, saying something really stupid. But it is the more general idiom and can mean both doing OR saying something stupid.

Hi Jesus, To "put your foot in it" means you've made a mistake (as in "I stepped in poop").

It depends on who is saying this to you and where. 1) It can mean you were being tactless or doing something embarrassing. 2) It can be a compliment to someone's cooking. Usually, it is said towards someone in the South (U.S.) who has made a really good meal.