The rapper tweeted out a response to a pic floating around the internet of DJ Boof -- the DJ on her "Pink Friday 2" tour -- putting a sharpie to a fan's boobs ... scribbling his name with a big ole grin on his face.

Boof says the fan asked him to sign her chest ... adding text to the post claiming he'd finally hit famous status -- 'cause people wanted his John Hancock on their boobs!

But, seems Nicki's not too stoked on Boof's newfound perks of the gig -- retweeting the pic on X and writing, "I promise I’ll fire him if I EVAHHHHH see this again. Df."

Unclear if Nicki's joking here or not ... but, she seems straight-up done with nonsense these days -- not surprising given the stressful weekend she just endured.

As we reported ... Nicki live streamed a run-in with Amsterdam police, who told her she was under arrest. She eventually made it out of custody with just a fine -- but, she had to cancel a show in Manchester, and she's none too pleased with how cops treated her in the Netherlands.

She even touched on the incident -- albeit briefly -- during her show in Birmingham last night ... and, she told fans she's going to fight tooth and nail against the cops in Holland.

So, maybe it's just a bit of stress coming out ... though Boof may want to keep his pen to himself for the time being.