A hero scrap metal worker has saved a four-year-old boy from choking on a marble just two days after he finished his first aid course.

Malcolm Wayman, from Wellington, was picking up sheets of metal when he noticed a woman in the car in front of him shaking a child in the front seat.

Unsure of what was happening, Mr Wayman kept an eye on the vehicle before it pulled in to a driveway and the woman rushed to pull the child out of the car.

The child was limp in her arms and she was screaming for help.

Malcolm Wayman (pictured), saved a four-year-old boy from choking on a marble just two days after finishing his first aid course

Mr Wayman was picking up scrap metal when he noticed a woman in the car in front of him shaking a child in the front seat

'She screamed, "Help me, help me, help me! My boy's not breathing",' Mr Wayman told Stuff.

Mr Wayman did not expect his first aid skills would be used just two days after he finished the course.

With the information still fresh in his mind, Mr Wayman sprung into action grabbing the child who was turning blue.

He discovered there was something in stuck in the child's airway, which he was unable to reach.

Mr Wayman then laid down the young boy across his knee, slapping his back five times, hoping for whatever was lodged in his throat to come out.

When nothing happened, Mr Wayman compressed the child's chest and back.

After the second time, a marble escaped his mouth and the boy started asking for his mum.

Mr Wayman found out the boy's name was Ben, and the mother was thankful he saved her son. He hopes to meet them once again

Mr Wayman found out the boy's name was Ben, and the mother was thankful he saved her son.

He said he didn't think other than the fact he had to do something because the boy wasn't breathing, Stuff reported.

Mr Wayman hopes to meet them once again.