背生芒刺 bèishēng-mángcì
[be in most uncomfortable position like having spikes in the back;feel prickles down one's back] 芒刺,草木、茎叶、果壳上的小刺。背上扎了芒刺,比喻极度不安。也说“背若芒刺”“芒刺在背”