This phrase has a negative tone and implies criticism or humiliation towards someone's past mistakes. After losing the game, the coach kept rubbing their nose in it, making them feel worse.
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Informal Use
It's an informal expression not suitable for formal contexts such as business meetings or academic papers. I wish office meetings weren't venues to rub someone's nose in it.
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Often Past Mistake
Usually refers to a past mistake or failure, not something done correctly or accomplishments. Even after a year, they love to rub his nose in that old budget blunder.