班门弄斧

班门弄斧 [bān mén nòng fǔ]

1. ■ display one's slight skill before an expert; be conceited; display one's incompetence before a connoisseur; go to teach hewing to the God of Carpenters; show off before a superior man; show off in the presence of an expert; show off one's proficiency with the axe before Lu Ban， the master carpenter; teach fish to swim; teach one's grandmother (how) to suck eggs:

先生大名， 如雷灌耳， 小弟献丑，真是班门弄斧了。 Your great name long since reached my ears like thunder. I am ashamed to show off my incompetence in the presence of an expert like yourself.