have a chip on your shoulder about something

Từ điển Oxford Advanced Learner 8th

have a ˈchip on your shoulder (about sth) idiom
(informal)to be sensitive about sth that happened in the past and become easily offended if it is mentioned because you think that you were treated unfairly
•He has a real chip on his shoulder about being adopted.
Main entry: ↑chip_idiom