The 43-year-old man allegedly punched a constable and was wrestled to the floor after refusing to provide identification when challenged for not wearing a mask on a train travelling between Gosford and Woy Woy on Saturday afternoon.

While on the ground, police allege he bit a constable twice on his stomach area and finger.

The constable suffered lacerations and bruising and was taken to Gosford Hospital for treatment before being released, police said.

His alleged attacker was arrested and taken off the train, where it is alleged he kicked out at police on the platform.

The man has since been charged with not wearing a fitted face-covering on public transport and assaulting a police officer causing actual bodily harm, among other offences.

The man was granted conditional bail and is expected to face Woy Woy Local Court next month.

The NSW government bowed to pressure in early January, following Sydney's northern beaches outbreak, making masks mandatory in certain settings across Greater Sydney, the Central Coast and Wollongong including on public and shared transport.

Australian Associated Press