Senior Sergeant Craig Brown, of Dunedin, said the boy suffered a serious laceration to a wrist, cuts to a leg and abrasions to his head.
Police were called to the incident on Brighton Rd, between Trecastell Rd and Taieri Mouth Rd, just before 1pm.
Mosgiel and Dunedin police units attended the scene and tended to the boy's injuries, Snr Sgt Brown said.
The Mosgiel unit then transported the patient to the Dunedin Hospital emergency department.
St John communications adviser Ian Henderson said the boy had earlier been transported a short distance in a private vehicle by a member of the public, before the driver called St John asking what to do.
It was decided the member of the public would take the patient to hospital, but police were called shortly afterwards to take over.
