A 21-year-old man required hospital treatment after the attack near the Stag Bar on Weavers Close on Thursday 22 December.
Police Scotland has released images of a man they wish to trace in connection with the incident.
They have asked him or anyone who might know him to come forward to assist with their inquiries.
He has been described as a black male, aged between 25 and 35 years old with short, dark hair, dark facial hair or a beard.
At the time of the incident, he was wearing a two-tone hooded anorak, dark trousers and dark footwear.
He was seen in the vicinity of the incident and also subsequently in the Townhouse Hotel.
It is believed that he may have links to the Liverpool or Manchester area.

The woman, who has severe learning difficulties, was held by Keith Baker and his wife Caroline at their County Armagh home.
She was found in a squalid room in the so-called house of horrors in 2012.
When she was rescued, she was severely malnourished and had lost almost all her teeth.
Police believe the woman was trafficked into Northern Ireland by Baker in 2004.
It is understood her husband reported her missing to police in Suffolk where they had been living.
A senior police officer said the repeated attacks on the vulnerable woman was the "most depraved and awful crime" he had ever come across.
The woman's torment was reported to police in 2012 by Mandy Highfield, mother of four of Baker's eight children.
Speaking exclusively to the BBC, Ms Highfield said she had to coax the Bakers' victim to leave when the police and social workers came to rescue her because the woman was too frightened to go.
Ms Highfield had lived with Baker, effectively as a second wife, and was the mother of four of his eight children: Caroline Baker was the mother of the other four.
Ms Highfield said Baker exerted complete control over everyone in his household.
"If we'd go out, he'd be as nice as pie and then, when we were on our own, he'd hit me because I'd been talking to people," she said.
"I wasn't allowed to talk to anybody or have friends or even talk to my family."
A tiny room in the house had been turned into a prison cell for the vulnerable woman, she said.
"Keith took the handle off the door. There was no light bulb in the light, no carpet on the floor, no curtains up against the window. It was like a little prison."
Talking about the sex abuse, she said: "How could they treat somebody like that - with a disability like she had?"
"It wasn't fair and I just couldn't handle it so I went to the police and told them. Then the police came down and they took me out of the house and talked to me.
"I told them everything. Then the social worker and the police went upstairs and saw the other woman in the bedroom.
"They took her out, but she didn't want to go because she was scared.
"I said to her: 'You've got to go; you can't live like this anymore.' Then she left with the police and the social worker."
Det Ch Sup George Clarke, head of the Police Service of Northern Ireland's Public Protection Unit, said his officers were shocked by what they uncovered at the Bakers' home.
"It became very clear to the detectives that it wasn't just a case of physical abuse but that there was a very depraved sexual element to this," he said.
"This woman was raped repeatedly by Baker who was aided and abetted by his wife.
"It would also appear that these assaults were on occasions recorded and we can only assume that was for the sexual gratification of Baker."
He said it was "almost impossible to estimate or imagine the suffering that she's gone through".
"The abuse and the fear that she was living with must have reached a stage where the grotesque, grotesque treatment and abuse became just her normal life.
"I think that in my time in the police I've never come across a crime that is quite so depraved and awful."
Police have released CCTV images as part of investigations into an assault outside an Arbroath bar last year.
[NEXT_CONCEPT]
A woman kept prisoner in a Northern Ireland house and repeatedly raped and assaulted for eight years was too afraid to leave when police came to rescue her.