Josh Corbeski, 15, was first on the scene when Daniel Ryan came off his bike in bushland at Mt Keira about noon on Saturday.

The 15-year-old, also from Figtree, over-cleared a jump and was sent flying over his handlebars, leaving him with back pain and tingling in his hands and feet.

Josh, who was riding behind, switched into emergency response mode, armed with the skills gained from studying for his First Aid Certificate at Figtree High School.

"I checked his eyes, they were really dilated," Josh said.

"He was conscious but when I asked, he couldn't remember where he was, what he was doing or what day it was.

"He had pain in his lower back and legs. He tried to get up, but I told him to stay still.

Daniel's father, who had also just completed a First Aid Certificate, arrived soon after and continued the care.

Police and ambulance responded as the Rescue 26 helicopter was called due to the teenager's remote location in rugged, steep terrain.

A paramedic was winched in, however the helicopter was called off when the warning light of the winch cable began flashing.

This left emergency personnel on the ground with the task of stretchering Daniel 1km out of the bush on a spinal board to a waiting ambulance.

He was taken to Wollongong Hospital, where he was diagnosed with concussion and held overnight for observation.

Josh said he studied first aid with St John Ambulance through his school's Links to Learning course.

He was grateful for being able to provide his friend with formal care, but played down his role in the rescue.

"I was just helping a mate," he said.

Wollongong District Ambulance manager Norm Rees praised Josh's efforts.

"He should be very proud of himself - there should be more people around like him," he said.

"Having a person with first aid knowledge makes a massive difference to us when we turn up at a scene.

"We can arrive with our 'you beaut' machinery, but unless first aid is done in the first instance ... it just gives the patient a better chance."