He was spotted lying on a road by a passer-by who called for help.
He was taken to hospital for treatment for a fractured jaw after the Hibson Road incident, but is now at home despite his serious injuries.
Lancashire Constabulary has revealed: “It happened at approximately 3-30pm on Tuesday, January 7th, 2014.
“An assault took place just off Edge End Lane, near to Marsden Heights Community College, Nelson.
“During the incident a 15-year-old youth was approached by a group of youths who attacked him, kicking him to the ground.
“He sustained a fractured jaw during the incident. He was found by a passer-by.”
And they added: “A number of lines of Inquiry are underway to identify the persons responsible for this unprovoked attack.”
The police are appalling for any witnesses to this incident to get in touch. They can be called on 101, or alternatively Crimestoppers, anonymously, on 0800 555111.
The victim’s older sister has praised those who helped in his rescue.
On Facebook she said: “I I would just like to say a massive thank you to the lady which is unknown who comforted and rang an ambulance for my little brother this afternoon around half past three in the Hibson Road, Nelson, area after he was brutally attacked by a gang of lads and left for dead unconscious in the road.
“We are so grateful and really appreciate what you did just goes to show there are still some kind-hearted people out there.”
The police are hoping to make arrests soon.