NSW teen on GBH charge for assault on man

A teenager has been charged with assaulting a 44-year-old man northwest of Sydney.

Police say an 18-year-old man and a friend became involved in an argument with the man as they left a train at Windsor Railway Station around 10.50pm on Friday.

The teenager is alleged to have punched the older man to the ground, leaving him unconsciousness, before he was assisted by a member of the public until emergency services arrived.

He was taken to Nepean Hospital and is to have facial reconstruction surgery.

Two men were arrested and taken to Windsor Police Station.

One man was released without charge while the 18-year-old was charged with recklessly causing grievous bodily harm.

He was refused bail to appear at Parramatta Bail Court on Saturday.