Police were called to Busticle Lane in Sompting on Sunday (November 4) to a man trying to get into a flat.
At around 11.45pm someone knocked on the victim’s front door and he answered it.
However the suspect asked for someone who didn’t live at the property and the victim went to shut the door.
As he did the suspect threatened him with a knife and stabbed him in the arm.
The 30-year-old victim was taken to hospital with a small cut to his lower arm.
The suspect is described as white, in his early 20s, medium build, curly short blond hair and around 5ft 8in.
He was wearing a blue bodywarmer, a navy blue jumper, denim jeans and had a local accent.
A police spokesman said: “We are appealing to anyone who saw a man in the road or let him into the block of flats around that time. Please come forward on 101 quoting 0031 of 5/11.”