The correct reading is ひにく. It's a compound of 皮 (ひ, skin) and 肉 (にく, flesh), both using their On'yomi, which metaphorically evolved to mean irony. Wrong readings like ひこう or ひにん misidentify 肉. 皮肉 refers to the use of words that mean the opposite of what is literally said, often to mock, or a cynical view of life.

正しい読みは「ひにく」です。皮(ひ)と肉(にく)の音読みから成り立ちます。他の誤読は漢字の形や音の混同です。皮肉は、文字通りの意味とは反対のことで相手を批判する、遠回しな言い方や態度を指します。