研究一下他為什麼咬手指。
我細仔喜歡"tear"手指甲,後來發現他無聊或緊張,就"tear"。若他因緊張,我不會話他,而是解決他緊張的事。但是因無聊,我會提出,叫他唔好。Actually he knows it not correct. He 奸笑when he find we discover he is tearing his finger tips!
You kid is only 3 may be a bit difficult to stop him. Try to remind him, 唔好駡。My boy is now 5 and some time he still tear but the frequency is decreasing.