Tony Hawk -- GNARLY LEG INJURY ... During Skate Accident

Ever wanted to know what the inside of Tony Hawk's thigh looks like? Well, now you can 'cause he RIPPED HIS LEG OPEN during a crazy skate accident in New Orleans.

The details surrounding the accident are unclear -- but here's what we know ... THERE WAS A GIANT BLOODY HOLE IN TONY'S LEG!!!!!

The good news ... he's been stitched up and even gave the ol' thumbs up sign to the camera.

He also tweeted, "Living the dream! (but today kinda sucked)"