Officers were called to Portland Street at 9.20pm on Saturday, August 28, following a report of an assault.
Nottinghamshire Police officers are continuing to investigate the attack, but said no arrests have been made.
They are appealing for anyone who may have witnesses the incident to contact them.
Inspector Neil Bellamy, from Nottinghamshire Police, said: “This appears to have been an unprovoked attack that left a man requiring medical treatment for a non-life threatening injury.”
Anyone who witnessed the attack is asked to call 101, quoting incident number 784 of August 28.