养痈遗患

yǎng yōng yí huàn

lit. to foster an ulcer and bequeath a calamity (idiom); tolerating budding evil can only lead to disaster

to cherish a viper in one's bosom

养

yǎng

to raise (animals)

痈

yōng

carbuncle

遗

yí

(bound form) to leave behind

患

huàn

to suffer (from illness)