BLOW HIS/HER OWN HORN
to display one’s achievements or good characteristics to make others feel bad
occasionally tooting or honking substituted for blowing.
There's also the idiom beat your own drum.
There is one more modern use that’s even more exotic. Every now and again you encounter “blow one’s own horn” used in an extended metaphor, which put as delicately as possible, refers to the act of autofellatio. (And no, that auto- has nothing to do with motor vehicles. :) Eddie Murphy famously said he’d never leave home if he could blow his own horn, and this is what he meant by the expression.
1. A: How is your new teacher?
B: He spent the first hour of class blowing his own horn by talking about his degrees, his books, his sports car and his beautiful wife. I dislike him a lot!
2. A: Did you get a good score on the TOEFL test?
B: I don’t want to blow my own horn, but I did fantastically!
3. Keith lets everyone know that the boss is going to make him the new assistant manager. He likes to blow his own horn.
4. Ruth won’t make many friends if she keeps blowing her own horn about her accomplishments.
5. The young woman blew her own horn by showing her expensive new iPhone to her jealous friends.
Dating back to at least the 16th century, this phrase is a reference to the practice of blowing horns to announce the arrival of important officials such as kings. To blow one’s own horn is to boast or claim a position of superiority over others.
Idiom: a group of words that means something different than the individual words it contains.
"Americans use about four idioms in every minute of conversation. If you don't see the light of American English Idiom, you're in the dark understanding American English!" Mentor Josephan P. Sterling Every day I will post a new Idiom, so stay tuned to Mentor Josephan's Idiom of The Day.
Are you ready to speak English or not!™