Bryden Parker, 24, Coulstock Street, Warrnambool pleaded guilty in the Warrnambool Magistrates Court to recklessly causing injury.

Police said that at about 8pm on December 16 last year the victim was at the Warrnambool breakwater with a friend and seven children when he was approached by Parker.

Parker claimed the man had slashed the tyres of his mother's car.

A witness videoed Parker as he punch the victim to the face, causing a bleeding cut inside his mouth.

During an interview Parker said his mother couldn't afford to buy Christmas present for her autistic son because her tyres had been slashed.

Parker said his actions were dumb, he was remorseful and it was an honest mistake.

He said his prior court appearance for assault arose out of a fight at a house party in which he became involved.

Magistrate Cynthia Toose said there had been a number of children nearby and people saw the assault.

"This incident would have frightened people," she said.

Ms Toose warned Parker if he returned to court for another offence of violence he would virtually be imprisoning himself.