William Moore and a friend were staying in Nyngan for work and were making their way back to the caravan park they were staying in at 1am on Sunday when Mr Moore was hit by an unknown man.

Mr Moore had surgery on his jaw on Monday afternoon.

His sister Ashleigh Moore said he had been left in considerable pain and faced a long recovery.

"Billy and his friend had been having a few quiet drinks at a pub but decided to leave when a young guy, who was about 18, started mouthing off at them. They walked back towards the Riverside Caravan Park where they were staying," she said.

"A man and a woman had been walking in front of them but they slowed down. The man abused Billy and then king hit him and then hit Billy's friend as well. Billy and his friend fled back to where they were staying."

Mr Moore went to Nyngan Hospital the following morning but was referred to Orange Health Service for x-rays on his jaw.

Those x-rays revealed his jaw was badly broken and he was taken to Westmead, where surgery was carried out.

"His whole face is swollen, and he is in intense pain. He will have to stay in Sydney for a couple of days and he has had to take eight weeks off work," Ms Moore said.

Mr Moore believes his attacker may have been heading towards the same caravan park.

"Billy said he recognised the woman from the caravan park and she had also been at the pub," Ms Moore said.

"He didn't get a good look at the man that attacked him because it was dark and happened so quickly."

After discovering the full extent of her brother's injuries, Ms Moore reported the incident to Orange police who referred the matter to Nyngan police, who are investigating the incident.

Anyone with information about the alleged assault should contact Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page:https://www1.police.nsw.gov.au/.