A northern beaches police officer used "significant" force on a man who later accused him of assault, a Sydney court has heard.

Leading Senior Constable Shaun Moylan is charged with assault causing actual bodily harm, over an incident in the charge room dock of Dee Why police station last April.

Mark Adamski said he was pushed twice, causing the back of his head to hit the wall.

The incident was captured by CCTV cameras.

Custody manager Senior Constable Daniel Gill told the court Moylan cupped his hand on Mr Adamski's neck at the time of the second push.

Asked how much force was used, Senior Constable Gill said "there was a significant amount".

He said Mr Adamski instantly started to complain about what had happened.

"Did he request medical attention?" prosecutor Andrew Wright asked.

"He may have, yes," Senior Constable Gill responded.

He said no medical assistance was provided but Mr Adamski was informed of officer Moylan's name and told he should return to the police station the next day if he wanted to make a complaint.

The court heard Mr Adamski asked for an ambulance earlier in the evening, for a minor cut to his hand, but it was deemed unnecessary.

Police describe Adamski as 'argumentative'

Mr Adamski previously told the court the alleged assault caused immediate pain and he took himself to Manly Hospital after being released from custody.

Another officer who witnessed the incident, Constable Brendon Kitchener, said he reported it to two colleagues, including Senior Constable Gill.

He described Mr Adamski as argumentative.

Senior Constable Gill said Mr Adamski "was attempting to antagonise Senior Constable Moylan".

The hearing will resume at a later date.