The actor, who plays Walford's Tyler Moon, has been accused of breaking 21-year-old Hayden Deol's jaw and injuring his cousin Sab Deol during an altercation at a nightclub in May 2011.
Southwark Crown Court today heard that Hayden Deol needed two metal plates fitted to his mouth following the alleged attack, This Is Local London reports.
Prosecutor Riel Karmy-Jones told the jurors that Discipline was at the Merah club in central London with EastEnders colleagues Shona McGarty (Whitney Dean) and Bunmi Mojekwu (Mercy Olubunmi) when he clashed with the two men.
It is alleged that Discipline lost his temper after Sab Deol made a jibe about his clothing.
Karmy-Jones told the court: "Hayden Deol was standing chatting to his friend along with his cousin Sab Deol when the defendant passed by.
"Sab Deol made a remark about [Discipline's] clothing, saying it looked like one of the shirts that Hayden wore to work. There is no doubt that this remark was somewhat derogatory and Hayden and Sab laughed."
The court heard that Discipline replied "in an aggressive way", which resulted in Hayden Deol pushing him with one hand in the chest.
Discipline allegedly then followed the pair into the club's VIP area, where the altercation continued.
Karmy-Jones continued: "The defendant accosted Sab and said 'Do you think you are funny?' He was angry and shouting when he said this and he then punched Sab twice in the face. Sab staggered backwards, dazed by the blow.
"The next thing that Sab saw was the defendant had moved over to Hayden and punched him. The punch was landed with such a force that he crashed back against the wall."
Discipline denies causing grievous bodily harm and common assault. The trial continues.