It happened at about 2am on Saturday, December 7 following a verbal altercation.
The victim suffered a cut to his eye and swelling in the attack.
British Transport Police have released images of a man they would like to speak to.
Anyone who recognises him is asked to contact BTP by texting 61016 or by calling 0800 40 50 40.
In both cases, quote reference number 1900105318.