An 18-year-old woman had been having a drink in the Bootlegger public house on High Street on Saturday, November 26.
She was assaulted by a woman she knew when she went to the toilet at some time between midnight and 12.25am.
Humberside Police today said the victim sustained facial and head injuries during the incident but did not seek any medical treatment.
A 35-year-old woman has been arrested on suspicion of assault and released on conditional police bail while enquiries continue.
Officers are now seeking independent witnesses to the assault.
Anyone with information should call 101, quoting crime reference number 2231450, or Crimestoppers anonymously on 0800 555 111.