Put your foot in it
Definition 1 of 1
Pro Tip 1/3Social Faux Pas
Understand that using this phrase often points to a social mistake that's awkward or taboo. 
When he mentioned her divorce, he really put his foot in it.
Pro Tip 2/3Apology Trigger
It's usually followed by an apology or an attempt to correct the awkward situation. 
After commenting on her haircut, he realized he'd put his foot in it and quickly apologized.
Pro Tip 3/3Informal Expression
It's an informal idiom, more likely to be used in personal conversations than in formal contexts. 
I didn't know he had failed his exams; I really put my foot in it.