An agricultural fencing boss who had a "cavalier" attitude to safety has been fined $22,000 after a young worker was blinded in his right eye.

Daniel Anderson, an agricultural fencing sole trader, had a 17-year-old worker who was chiselling when a piece of metal flew into his right eye.

The teenager lost the sight in the eye despite multiple surgeries.

Anderson did not report the injury to WorkSafe as required by the Health and Safety at Work Act 2015.

Several months later, the victim's mother did so and triggered an investigation.

When asked whether he told workers to use protective gear, Anderson's response was: "I'm not their mother and going to dress them every morning."

He said he did not provide full instruction to the victim on personal protective equipment such as safety glasses because "It was common sense".

PPE was too expensive and "I'm too small for that sort of... carry on," he told a WorkSafe inspector.

Anderson's comments reflect an "outdated, unacceptable, and cavalier attitude," WorkSafe's national manager of investigation Hayden Mander said.

A young man at the start of his working life has lost sight in one eye, he said, and it was "astounding" that his employer did not understand the seriousness of the situation.

Anderson was ordered to pay $22,500 to the victim for emotional harm and losses.

He was convicted on two charges - failing to ensure the health and safety of his workers and exposing them to risk of serious injury, and failing to report the injury.

He faced a maximum fine of $10,000 for each charge, but Kaikōura District Court Judge Raoul Neave said the man did not have insurance and was unable to pay a fine

Workers who are vulnerable because of age, inexperience, or conditions of unemployment may be less likely to question health and safety practices, or to speak up if they are unsure, WorkSafe said.

It is illegal and wrong for an employer of any size not to report an incident like this, Mander said. "No employer is exempt."