A GUNS N' ROSES fan was hit in the face by AXL ROSE'S cordless microphone during a show in Australia over the weekend . . . and it busted up his mouth.  His two front teeth were damaged, he got a cut lip, and his mouth was bleeding.

The fan 39-year-old "pest controller" Darren Wright says, quote, "With the bright lights and explosions, I couldn't see anything.  The next thing I knew, I was whacked in the mouth.  I thought I had been punched .

"It took a few seconds to realize what was going on.  I could feel bits of teeth in my mouth.  Then someone is climbing through my legs to grab the microphone."

He doesn't think Axl intended to do it . . . but he still wants someone to pay to have his teeth fixed, so he's preparing a lawsuit.  A dentist told him it would require months of dental work, which would run him at least $5,000.

No one from Guns N' Roses has commented but Wright says a tour promoter called him to apologize, and offered him a microphone signed by Axl.

That's nice.  But Wright says instead of a MEMENTO, he'd rather have CASH.  He says, quote, "In reality, I don't think the microphone is going to fix my teeth or pay for the dentist.  I'm a father of four on a single income."

Regardless, he's says he doesn't, quote, "harbor any ill-feelings."  

Well yeah, if you rode it out for 15 years waiting for "Chinese Democracy" . . . and it satisfied you enough to remain a fan five years later . . . what's a few chipped teeth right?