Referee Mike Dean was cut on the forehead by a coin thrown from the crowd during a thrilling south Wales League Championship derby between Cardiff City and Swansea City which ended in a 2-2 draw on Sunday.
Police arrested a fan for throwing the coin and Cardiff chairman Peter Ridsdale said he would be banned from the club's home matches for life if found guilty.
"There is absolutely no place in football for anyone like that," Ridsdale said. "We don't want people like that anywhere near Cardiff City. I have apologised to the referee on behalf of the club for what happened."
The high-profile match, probably the last derby to be played at Ninian Park before Cardiff move to a new stadium, began at 1000 GMT with dozens of police present to prevent trouble among the bumper 20,000-plus crowd.
Cardiff, who last played in England's top division in 1962, and Swansea, last in it in 1983, are both chasing promotion via the playoffs.