A unnamed supporter was identified, arrested and has since been charged by South Wales Police and is due to appear in court on Monday, April 20.
But Cardiff, who have been plauged by a hooligan reputation in the past, could now face further remand from the FAW, although the association have refused to put a timescale on when a decision will be made.
Meanwhile, PGMO (Premier Game Match Officials) have confirmed the matter is now in the hands of the FAW and the police.
The statement read: "Mike Dean was well looked after by the medical staff at Cardiff City after been injured by a coin thrown by a spectator.
"The matter is in the hands of the Police and the referee has filed his report with the Football Association of Wales."
A man has been charged over the incident, police said.
South Wales Police confirmed on Monday a 24-year-old man from Pontypridd has been charged in connection with a missile-throwing incident.
He was released on bail to appear at Cardiff Magistrates Court on April 20.
Police made six other arrests outside the ground after the match, five relating to public order offences and one for breaching a football banning order.
Of those involved, three were from Cardiff, one from Ebbw Vale, one from Blackwood and one from Abertillery.