小洞不堵，大洞吃苦 [－－－－－－－－－]

Jyutping siu2 dung6 bat1 dou2 , daai6 dung6 hek3 fu2
Pinyin xiǎo dòng bù dǔ , dà dòng chī kǔ

Definitions (CC-CEDICT)
  1. lit. a small hole not plugged will give you grief when it gets bigger (idiom)
  2. fig. a stitch in time saves nine