A: I want to help Johnny out on his project, but I know he’s very proud, and I don’t want to step on his toes in any way.

B: Have an open conversation with him in private. I believe he’ll appreciate your consideration.

Note:

This idiom means “to insult, offend, or upset someone, especially by involving oneself in that which is someone else’s responsibility.” The analogy between physical and emotional pain here is obvious. In American English, people say “step on one’s toes” while in British English, they say “tread on one’s toes.”