Police are appealing for dashcam footage of the attack on Woodville Road, Guildford, where a Toyota Starlet which was being driven north, was cut off by a white Toyota Hilux WorkMate about 4pm.
The male driver of the Hilux exited the vehicle and approached the Starlet, where he confronted a 19-year-old man in the front passenger seat, before producing a small knife and stabbing him in the arm.
The man then returned to the Hilux before driving into Oxford Street.
The driver of the Starlet, a 20-year-old man, was not hurt and drove the 19-year-old man to hospital for treatment of a stab wound to his right bicep.
Cumberland Police are investigating and appealing for witnesses or anyone who has dashcam or mobile phone footage to contact them or Crime Stoppers on 1800 333 000.
