Leigh Ettridge, 32, was at Mojo Pool Lounge and Bar in Armstrong Street when he injured the victim, causing him to lose consciousness for a short time.

The victim was taken to hospital by ambulance where he was diagnosed with a fractured nose or bruising.

Ettridge's lawyer said her client was with his former partner at the lounge when another person offered her drugs, to which he reacted poorly.

"This is a once off incident. He has no prior (charges)," the lawyer said.

Ettridge pleaded guilty to recklessly causing injury at Ballarat Magistrates Court on Thursday.

Magistrate Gregory Robinson fined him $2500 with conviction.

He said he would have jailed him for six months if it wasn't for his guilty plea.