University of Otago exchange student Zach Kornse borrowed his flatmate's bike to ride the two blocks from his Castle St flat to the campus on Wednesday afternoon.
But when the American lifted the bike's front wheel to cross a speed hump on the campus, the wheel detached itself.
The bike's forks hit the tarmac and he flipped forward.
''I landed directly on my face ... I can't remember any of it because I hit my head so hard.''
After lying unconscious for seconds, he woke in ''a puddle of blood'' and heard Campus Watch staff ''going all crazy''.
''They were telling me to hold my nose and I had no idea where I was.''
Campus Watch staff drove the New Jersey man to Dunedin Hospital's emergency department.
The cut on the bridge of his nose needed three layers of stitches.
His upper lip needed four stitches and the inside of his lip needed another five.
A front tooth had been pushed backwards and needed to be splinted to another tooth.
He had not worn a helmet because his flatmate did not own one.
Zach obtained CCTV footage of his fall and posted it on Facebook on Thursday and within 12 hours it had been viewed more than 6000 times.
He posted it to show the ''gnarly crash'' to friends back home.
People had been stopping him on campus to photograph his face.
''It's like I'm a little celebrity for a moment. Everybody wants a picture.''
Zach began his one-year exchange in February and his father, Pete Kornse, arrived in Dunedin yesterday for a South Island tour the pair had planned.
Zach's 20th birthday is today and the pair are planning a low-key celebration tonight.
Once he heals, Zach plans to get back on a bike ''and hopefully forget that it happened''.
