A 21-year-old man from Hove was treated in hospital for a burst blood vessel after being attacked in Brighton.
The attack happened outside Revolution in West Street, Brighton, in the early hours of Wednesday (27 April).
Another man who had also come form inside Revolution grabbed the victim’s arm and punched him in the face, causing him to fall backwards and hit his head on the pavement.
The victim was taken to the Royal Sussex County Hospital, Brighton, with a burst blood vessel causing swelling to one of his eyes and cheeks.
Detective Sergeant Steve French said: “This was a vicious and unprovoked assault.
“There are a number of people around the entrance to Revolution at the time of the assault who I would like to speak to.
“The licensees of the venue are continuing to assist police in this investigation.”
The suspect is described as white, 5ft 10in tall, in his twenties, of a slim muscular build, with short mousey hair and slight facial hair.
He was wearing a blue round-neck long-sleeved T-shirt, dark jeans and white laced trainers.
Anyone with information about the attack, which happened at about 1.30am on Wednesday, is asked to contact Sussex Police on 0845 6070999.