The Worksop teenager was attacked while on his way home at around 7.45pm on Monday January 18th.
Three men had attacked him from behind as he crossed a field near the railway line and junction of Blyth Road and Carlton Road.
One of his attackers used a plank containing a nail to hit him near his left eye, puncturing the skin.
He was left unconscious and was taken to hospital for treatment.
Anyone with any information is asked to contact PC Kelly Stevens at Worksop Police Station on 0300 300 99 99, or call Crimestoppers, anonymously, on 0800 555 111.