nip something in the bud idiom
把…消灭在萌芽状态，对…防患于未然
to stop something before it has an opportunity to become established
Many serious illnesses can be nipped in the bud if they are detected early enough. 如果及早确诊，许多恶疾可以治愈。
It's important to nip this kind of bullying in the bud. 重要的是及早制止这种欺凌弱小的行为。