sore point
noun [ C usually singular ] uk/ˌsɔː ˈpɔɪnt/ us/ˌsɔːr ˈpɔɪnt/
C2 （不愿提及的）痛处，心病
a subject that someone prefers not to talk about because it makes them angry or embarrassed
Don't ask him about the job search - it's a bit of a sore point. 别问他找工作的事情——都成了他的心病了。