The victim required hospital treatment and also suffered damage to his teeth and bruising after the assault, which took place just before 5am on Sunday, July 10.
British Transport Police has released a CCTV image of a man they wish to speak to in connection with the incident.
The victim, from Brentwood in Essex, was waiting with a group of friends for a taxi when he was approached by a group of men who asked if they could push in front of them to get a taxi to Preston. When the victim refused he was punched in the face by one of the men in the group.
PC Cara Woolley said: “This was completely unprovoked and violent behaviour which is totally unacceptable. The victim’s attacker was extremely aggressive and was unwilling to wait his turn in the taxi queue which was only small with a wait of around ten minutes.
"It’s vital we trace the person responsible; if you recognise the man pictured, who we believe may be from Preston, please contact us. “
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference 126 of 25/7, or to call Crimestoppers on 0800 555 111.