芒刺在背

mángcìzàibèi
  1. feeling brambles and thorns in one's back (idiom)
  2. uneasy and nervous
  3. to be on pins and needles

CEDICT

to be jittery; to be on pins and needles

Wiktionary

比喻因畏忌而極度不安。《漢書．卷六八．霍光傳》：「宣帝始立，謁見高廟，大將軍光從驂乘，上內嚴憚之，若有芒刺在背。」《新唐書．卷一二一．崔日用傳》：「然每一反思，若芒刺在背。」也作「背生芒刺」、「背若芒刺」。

重編國語辭典

Entry Composition

1 芒刺 mángcì prickle; thorn; spine; sharp bristle
2 在 zài
  1. to exist; to be alive
  2. (of sb or sth) to be (located) at
  3. (used before a verb to indicate an action in progress)
3 背 bèi
  1. the back of a body or object
  2. to turn one's back
  3. to hide something from
  4. to learn by heart
  5. to recite from memory
  6. (slang) unlucky
  7. hard of hearing