臍ほぞを噛かむ

expression, godan verb (-mu)

regret bitterly; be very sorry

Idiomatic expression literally meaning 'to bite one's navel', used to express deep regret over something that cannot be undone. Often used in the phrase 臍を噛んでも及ばない (it's no use crying over spilt milk).

• 今いまさら後こう悔かいしても臍ほぞを噛かむだけだ。

  Regretting it now is just biting your navel; it won't change anything.

• あの時ときちゃんと勉べん強きょうしておけばよかったと、臍ほぞを噛かむ思おもいだ。

  I bitterly regret not having studied properly back then.