sore point ,
sore spot ,
sore subject

Parris could see she had brought up a sore subject.

It was a sore subject with all career military sorts.

"Jim, that is a very sore subject with medical men."

She sensed that this was a sore subject, and dropped it.

Apparently, in my efforts to make certain that you two are happy, I've instead simply stumbled upon a sore subject.

I reached only 5 feet 2, and it's a sore subject.

I know this must always be a sore subject with the family; let us say no more about it.

The law was overturned in court but is still a sore subject.

I'm delving into what can be a very sore subject for some people.

The idea that the fight for justice killed Cairo is clearly a sore subject.