噬脐何及 shìqí-héjí
[useless to regret;repent too late as one who is unable to bite one's navel] 噬:咬;及;到。当后悔时,像用嘴咬不着自己的肚脐那样,没有用的。后来就用“噬脐何及”比喻后悔也来不及