The attack happened at Ballymaglave Court, Ballynahinch, yesterday, Sunday, October 21.
A report was received that three men pushed their way into a flat in the area at around 2pm on Sunday and assaulted the male occupant, leaving him with a cut to his head requiring medical treatment.
A short time after the assault, four men were arrested in connection with the incident, at a house at Antrim Road in Ballynahinch.
One man was later released unconditionally whilst three others were interviewed then released on bail pending further police enquiries.
The investigation is ongoing and officers would ask anyone with any information about the incident to contact them in Downpatrick on 101 quoting reference number 811 21/10/18.
Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.