a sore point

sore point

A topic that makes one angry or uncomfortable. Whatever you do, don't mention his ex-wife—his divorce is really a sore point with him.
See also: point, sore

a sore point

or

a sore spot

COMMON You can say that a subject is a sore point with someone or a sore spot for them if it makes them feel angry, embarrassed, or upset. The continuing presence of foreign troops remains a very sore point with these students. Slow job growth is a sore spot for the US President. Note: If you touch or hit someone's sore point or sore spot, you mention a subject which makes them feel angry, embarrassed, or upset. The mention of Jim Kennerly had touched her sore spot. It was clear by his expression that my question had hit a sore point.
See also: point, sore

a ˌsore ˈpoint (with somebody)

a subject or matter that makes somebody feel angry or hurt: The tax increases are a sore point with Jake, as he’s going to lose a lot of money.
See also: point, sore
References in classic literature ?
It is a sore point with me, this being told what I am to do or not do by you self-constituted lords of creation.
Philip saw that the rivalry was a sore point with the old man.
Tulliver manifested an unusual discretion, because she had recently had evidence that the going to school to a clergyman was a sore point with Tom, who looked at it as very much on a par with going to school to a constable.
The affair of the chaplaincy remained a sore point in his memory as a case in which this petty medium of Middlemarch had been too strong for him.