tread on someone's toes
tread on (someone's) toes
To insult, offend, or upset someone, especially by involving oneself in that which is someone else's responsibility. I want to help Johnny out on his project, but I know he's very proud, and I don't want to tread on his toes in any way. Look, you're going to have to tread on a few peoples' toes if you want to get ahead in this business.