The assault happened at around 1.10am on Saturday March 23, outside of The Association bar in Ripley, Derbyshire.
Detectives are appealing for witnesses, as well as any CCTV or mobile phone footage.
The attacker is described as a man in his twenties, of slim build and with a shaved head. He was wearing blue jeans and a red t-shirt.
Detective Sergeant Sean Grainger, who is leading the investigation said: We are aware that there were a number of people in the area at the time of this incident and understand that some of them may have been recording it on their phones.
“I’d urge anyone with such footage to send it to police, as soon as possible, as this will assist us with our enquiries.
“We are still working to establish the exact cause of the victim’s injuries, but given the nature of them what we can say is that it’s clear some form of sharp object was used during the incident.”
Officers said the victim's injuries were described as ‘minor’ because they are not life-threatening and the victim was discharged from hospital a number of hours after being admitted.