A man was assaulted outside Remi’s pub in Silver Street, Kettering.
The incident happened between 11.45pm on Saturday, 4 March and 1am on Sunday, 5 March.
The 28-year-old victim was head-butted in the face, causing a broken nose.
The offender is described as black, in his late twenties with a stocky build and short black hair. He was wearing a grey, long-sleeved jumper with a black and grey camouflage pattern on the sleeves, dark blue jeans and blue suede lace-up boots.
Officers have arrested a man in connection with the offence, who is currently on bail pending further inquiries.
Anyone with information should call Northamptonshire Police on 101 or Crimestoppers, in confidence, on 0800 555111.