To rub salt in a wound is an idiom that means to purposefully make a bad situation worse.

在伤口上撒盐是个习惯用语，意思是故意让情况更糟糕。

But do not think rubbing salt in a wound will help. Doing that would be painful and not heal the wound.

但不要认为在伤口上撒盐能起到作用，这样将会很痛苦，而且不能愈合伤口。