compunction
A feeling of guilt when you know you did wrong.
Compunction is a feeling of guilt or uneasiness about doing something wrong. When you feel compunction, your conscience is bothering you. You might feel compunction about lying to a friend, even if the lie seems small, or about taking credit for someone else's work.
The word often appears in its negative form: someone acts “without compunction” when they do something questionable and feel no guilt about it. A student who copies homework without compunction doesn't feel bad about it at all. A bully who teases others without compunction has no guilty conscience stopping them.
Compunction is that uncomfortable twinge you get when you know something isn't right, even if no one else sees what you're doing. It's the feeling that makes you hesitate before doing something you know you shouldn't. Some people ignore their compunction and do wrong things anyway, while others let that guilty feeling guide them toward better choices. Having compunction means your conscience is working, alerting you when you're about to cross a line or after you've already crossed it.