eat humble pie

eat humble pie — каяться, виниться, признавать свою неправоту
If you eat humble pie, you admit that you are in the wrong and behave apologetically.

For example:

... Jim had to eat humble pie after we proved that what he'd said was wrong. (englishclub.com)

...Some politicians are so arrogant that they won't eat humble pie even when it's clear they've made a mistake. They just say they were "misinformed". (englishclub.com)

I found an intersting information about etymology of this expression.

"There is a catch in this one. It has nothing to do with humble. When a deer was hunted and killed the lords and ladies ate the flesh, or venison and the servants and followers made a pie out of entrails, and the Saxon word for the entrails of deer was 'umbles'." (From The Beginning of Words (How English Grew) by Colin Pickles and Laurence Meynell)

see also
[eat crow]