put on airs

(verb) to pretend to be more important than you really are

Example Sentences:

The new boss put on airs by lying to his employees about things he had done in the past.

A: Did you know that I was once the best football player in my school?
B: Really?
A: Yeah. I was captain of the team and everything!
B: How many students were in your school?
A: Um, 100.
B: Stop putting on airs, I bet anyone could have been the captain!

Media:

Similar idioms:

1. best bet
2. you bet your ass
3. give it a rest
4. put one’s money where one’s mouth is