玻璃心 Bōlí xīn
lit. heart made of glass (fragile)
Bōlí: glass. xīn: heart.
It metaphorically refers to a person whose heart is as fragile as glass and is easily hurt/offended by what others say. You can say, 他很玻璃心 Tā hěn bōlí xīn. to describe people who often feel offended and upset by others’ words.
Pinyin: Bùyào hé háizi kāiwánxiào, tā yǒudiǎn bōlí xīn.
English: Don't joke with the child, he would feel offended.