step on someone's toes

step on (one's) toes

To insult, offend, or upset one, especially by getting involved in something that is one's responsibility. I want to help John out on his project, but I know it's his baby, so I don't want to step on his toes in any way. Look, you're going to have to step on a few peoples' toes if you want to get ahead in this business.
See also: on, step, toe
Farlex Dictionary of Idioms.

step on someone's toes

Also, tread on someone's toes. Hurt or offend someone. For example, Be careful what you say about her losing weight; don't step on her toes, or Would I be stepping on someone's toes if I asked to help out with the party arrangements? This metaphoric idiom transfers physical to emotional pain. [Late 1300s]
See also: on, step, toe
The American Heritage® Dictionary of Idioms by Christine Ammer.

step on someone's toes

or

tread on someone's toes

COMMON If you step on someone's toes or tread on their toes, you offend them by interfering in something that is their responsibility. `Small shopkeepers know who sells what,' Sue explains, `so they don't step on one another's toes.' She's already seeing Dr Simmonds — I can't tread on his toes. Note: You can also say that someone steps on toes or treads on toes. It was no wonder, with such a complicated system, that I was stepping on toes from morning to night.
See also: on, step, toe
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • step on toes
  • tread on (someone's) toes
  • tread on somebody's toes
  • tread on someone's toes
  • no offence
  • no offense
  • fire questions, insults, etc. at somebody
  • tell a (little) white lie
  • fire insults at (one)
  • hurl insults (at one)