But Stephanie Green said it was her "dream come true", reported BBC.
Green was bruised but unharmed when Levine, frustrated by a broken PA system, hurled his mic into the audience, accidentally hitting her.
The frontman immediately apologised to Green, bringing her up on stage and hugging her.
"It's just literally the best day," she said.
Green and her sister had secured top-of-the-range front row seats for Monday night's concert at the Air Canada Centre in Toronto.
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"In my flustered state, I might have thrown my microphone on the ground and then it might have bounced off of the ground, into poor, sweet Stephanie's face," Levine said after rushing to Green's side.
"I felt so utterly terribly that I had perhaps wounded this young fan," added the singer, who is a coach on the US version of The Voice.