sore point

Translations
больная точка
The topic of his failed business is a sore point for him.
Тема его неудавшегося бизнеса — это больная точка для него.
Definitions
A sore point refers to a sensitive topic or issue that causes discomfort, irritation, or emotional pain when discussed or mentioned.
Words
point

noun
точка
sore

adjective
больной