He suffered a deep cut to the back of his head during the incident inside Manana Manana on Bradford Row, Lazarus Court, Doncaster, just after 11pm on Saturday, May 11.
The 27-year-old was taken to Doncaster Royal Infirmary but has since been released.
South Yorkshire Police said the bar was ‘cleared’ while officers carried out initial enquiries.
No arrests have yet been made.
Anyone with information should call South Yorkshire Police on 101 and quote incident number 1,007 of May 11.