Nottinghamshire Police are appealing for witnesses of the attack on a 57-year-old man in the car park of Lidl, near Carlton Road.
The man was hit several times with a D-ring bike lock outside the supermarket at around 4:15pm on Friday 1 February.
Police believe there to have been numerous shoppers who may have seen the incident when it occurred and are urging anyone with information to come forward.
A 37-year-old man has been arrested and questioned in relation to the incident and is currently out on police bail pending further enquiries.
Police are urging witnesses or anyone with information to call Nottinghamshire Police on 101, quoting incident 582 of 1 February 2019 or calling Crimestoppers anonymously on 0800 555 111.