Senior Sergeant Brad Burnett said the accused (20) and the victim faced each other in the ring at the local gym on February 16.
The session became heated leading spectators to enter the ring and separate the two. The pair then left the centre.
“The victim got into a car with his dad,” Sen-Sgt Burnett said.
“About 10 minutes later, the alleged offender got into his car.
“He came across the victim, pulled up alongside him and cut him off on Hester Avenue in Clarkson.”
Having forced the car to stop, Sen-Sgt Burnett alleged the man verbally abused the father and son, before punching the victim in the face, breaking his jaw.
The injury required metal plates to repair the damage.
Police charged the man on February 24 with grievous bodily harm, which carries a maximum prison sentence of 10 years.
He is due to face Joondalup Magistrates Court on March 23.