What should I do if my girlfriend pinches me really hard?

My girlfriend pinches me really hard and it hurts. I can take it like a man but it still hurts. Sometimes I pinch back and then she hits me so I pinch back and then she hits be harder which ends up in a fight. She then tells me that I am a man and suppose to take it. Feel free to ask me any questions.
What should I do if my girlfriend pinches me really hard?
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