The victim was walking home from town with his girlfriend when the attack happened, between 2:50am and 3:10am on Saturday, March 16,
A police spokeswoman said: "After turning into Lorne Road they were followed by a group of three men and one woman. The group then chased the victim into Lawrence Court where they attacked him."
The group ran away, in the direction of Barrack Road.
Anyone who witnessed the incident or has any information about it is asked to contact Northamptonshire Police on 101. Alternatively, they can call Crimestoppers anonymously on 0800 555111.