Eastenders star Tony Discipline appeared in court on Monday to face allegations he broke a man's jaw at a London nightclub last year.
The actor, who plays Tyler Moon in the soap, is accused of losing his temper and punching clubber Hayden Deol after he heard the man and his cousin laughing at his T-shirt.
Discipline, 23, was partying with fellow castmembers when the alleged incident took place at the Merah hotspot in May 2011.
Eastenders' Tony Discipline has appeared in court after allegedly breaking a clubber's jaw
Hayden told the jury he became concerned after seeing the actor "getting in my cousin's face" - and he then found himself caught up in the drama.
The 21 year old said, "It was a forceful punch and I was knocked off balance.
"I was a bit dazed and a bit shocked so I grabbed a friend to come to the toilet so I could check my face out because I could see I was bleeding.
"I could see blood coming out of my mouth and I could feel that my jaw was dislocated."
Hayden needed titanium plates inserted in his jaw and alleged the injury was so severe he still has pain when talking or eating.
In a police interview, Discipline said he acted in self-defence "to protect myself and escape".
Discipline denies grievous bodily harm and common assault and the trial, at Southwark Crown Court, continues.
Actresses Shona McGarty and Bunmi Mojekwu, who were with Discipline at the club, are due to give evidence.