The 23-year-old walked into the Right Price Retail shop, on Cavendish Walk, on Thursday, January 6, shortly before 2.50pm.
Staff called emergency services and officers attended and took the man to hospital.
It is understood he may have been assaulted at a flat in Pegasus Court, Welbeck Road.
His injuries are not believed to be life threatening or changing.
Anyone with information is asked to call Derbyshire police on 101, quoting reference number 220*10249.
To report information anonymously, call Crimestoppers on 0800 555 111.
If you have footage that may be useful for officers, please ensure it is securely downloaded to another device and kept safely for police to view.