A group of men became abusive and assaulted the staff, who were working at Rewind, in Carlton Road, at around 1.25am of Saturday November 13.
One of the doormen was injured.
Around 25 minutes later the same group returned in a car and threatened the pair again.
Detective Constable Jann Olsen, from Nottinghamshire Police, said: “It is disgraceful that someone going about their normal day’s work has being subjected to abuse and threats.
“In particular, the injuries sustained accompanied with racial abuse is unacceptable.
“We hope our quick action to arrest and interview four men offers the public reassurance of just how seriously we take incidents such as this, and local officers will continue to be in the area and available to talk to anyone with information or concerns.
“The men have been bailed with conditions and our enquiries continue.
“We would urge anyone who was in the area at the time, witnessed the incident or has any information to get in touch with us on 101, quoting incident 57 of 13 November 2021.”
Alternatively call Crimestoppers anonymously on 0800 555 111.