吃後悔藥 [－后－药]

Jyutping hek3 hau6 fui3 joek6
Pinyin chī hòu huǐ yào

Definitions (CC-CEDICT)
  1. (fig.) to regret (doing sth)
Definitions (Wiktionary)
  1. verb, figuratively, idiomatic
    to regret; to cry over spilt milk