Nick Jonas Has Bloody Good Time with Mystery Brunette in Australia

Nick Jonas isn't gonna let a little thing like an open wound on a hot chick's knee crush his game, as proven by this footage of their epic day ... complete with public makeout sesh.

Nick and his bro Joe are gallivanting around Australia this week, but Nick went solo on Wednesday for a hot date that got off to a rough start when his date banged up her knees during a bike ride.

Not to worry, he rescued the sexy sheila (Aussie for babe) in distress by sweeping her off her feet -- and gnarly knee.

Nick and his chick did lunch, did the beach, did a romantic nightcap at Sydney's Watson's Bay Hotel -- then, most likely, did each other.

They didn't even try to hide their hot and heavy hook-up, and we're told they left together after the place cleared out.