A man who crashed his trail bike, striking his groin on the handlebars, is lucky he wasn't injured somewhere more private.

The 39-year-old Warkworth man lost control of his bike while riding on a dirt track in Hira, about 15km northeast of Nelson, this morning.

Life Flight Trust rescue helicopter crewman Logan Taylor said the man had been riding quite slowly "and just fell off".

"He lost control at a low speed and the handlebar went into his groin area. It was actually just off to the side of the groin area, the upper thigh area - it wasn't quite in the private parts," he told APNZ.

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The man was treated at the scene by St John ambulance staff, but Mr Taylor said it would have been quite an effort to take him back down the track.

The Wellington-based Westpac rescue helicopter was called in about 10.40am to winch him off the track.

Despite the sensitive nature of the injury, the helicopter rescue harness was not too uncomfortable.

"I think he was alright because it just sits under your bottom, it doesn't actually go around your groin as much - you sort of sit down on it," Mr Taylor said.

The man was flown to Nelson Hospital to be treated for his injuries.

- APNZ