He dug out an area in the snow to make Mr Lightbody more comfortable before going for help.
Mr Lightbody, a Melbourne IT consultant, was carried down the mountain in a sled on the back of a snow groomer before the Youthtown Trust rescue helicopter transferred him to Waikato Hospital.
"I was in first-stage hypothermia by then and was shivering uncontrollably, and they couldn't give me anything for the pain, so it was pretty harrowing," he said.
He now faces surgery on his right ankle, which may be done in Melbourne.
Mr Lightbody said he was a keen cross-country telemark skier, which involved long and narrow skis where the heels lift up, but has been told he could have lasting ankle damage that may make it difficult in the future. But he was relieved to have avoided a potentially fatal knock to the head.
Mr Lightbody said he had been skiing in the South Island earlier in the year and was keen to return to New Zealand with his family next year.
Ruapehu Alpine Lifts marketing manager Mike Smith said it was amazing Mr Lightbody hadn't suffered more serious injury after falling such a distance.
The temperature on the mountain had been about minus 5C with a wind chill of minus 15C.
"You wouldn't want to be out in those conditions for too long," Mr Smith said. "He's pretty lucky, really."
Mr Smith said it was unusual for one person to have a large fall during a season, let alone two people in two days.
Aucklander Andrew Blair, 37, is in a stable condition in Rotorua Hospital after falling 60m down the mountain "like a rag doll" on Saturday. He had reached the Tahurangi Peak when the strap on his ice axe broke and he slipped on the snow face at an altitude of about 2600m, breaking his left leg.
In the South Island, a climber survived a 300m fall in the Mt Somers-Stavely area, southwest of Christchurch, on Sunday.
- ADDITIONAL REPORTING: NZPA
