A melee ensued as assistant referees Hamish McKenzie and Roly Senior stepped in to take control. The man was then returned to the group he was with, Corlet said.
Corlet said the man "was a member of the Old Boys club", but was not involved in Saturday's game.
Kingan later appeared shaken by the incident but declined to comment.
North Otago Rugby Union chairman Warren Prescott confirmed the rugby union had launched an investigation into the incident.
North Otago Rugby Referees Association president James Symes declined to comment, but said it "took the shine off two great games of rugby" on Saturday.
Old Boys president Richard Umbers was at the game but did not see the incident.
"I'm not going to deny it happened but I actually had my back to it," he said.
Umbers was not aware if the man at the centre of the incident was a member of the Old Boys club.
Valley president and North Otago refereeing stalwart Tim Petrie witnessed the incident but said it was not appropriate to say too much.
"I saw it happen, and it will be dealt with," Petrie said.