Bailey Martin (23) and the 19-year-old victim were strangers to each other before the attack in west Dublin, a court heard.
Martin, with an address at John’s Wood West, Clondalkin, admitted assault causing harm to the man and producing a knife in the course of a dispute on November 12 last year.
Judge Gerard Jones adjourned sentencing for the production of a victim impact report.
Blanchardstown District Court heard the incident happened at Tesco car park, Convent Road, Clondalkin.
Garda Sergeant Maria Callaghan said a medical report on the vicitm’s injuries was available and had been submitted to the court.
Garda Alan Lagrue of Clondalkin station gave an outline of the prosecution’s evidence so the judge could consider whether to accept jurisdiction.
He said gardaí arrived at the supermarket car park in response to a report of an “armed incident.”
The gardaí met the victim who had suffered a stab wound to the right side of his leg.
The man was taken to Tallaght Hospital, where he received three stitches before being discharged shortly after, Gda Lagrue said.
The victim did not know the accused before the assault, the court heard.
There were a number of friends with him at the time but they were not involved.
Gardaí made a number of enquiries, obtained CCTV and took witness statements.
The accused was arrested at his home on November 20 and brought to Clondalkin garda station, where he was detained for a number of hours and charged.
He was then taken to the Criminal Courts of Justice, where he was given conditional bail after a hearing, Gda Lagrue added.
Judge Jones accepted jurisdiction after hearing the summary of the case.
Prosecution evidence had been disclosed and handed over to the defence, Sgt Callaghan said.
Martin “would like to mark a plea,” his lawyer said, asking the judge to adjourn sentencing for reports to be obtained by the defence.
The injured party would also need to be canvassed for a victim impact statement, the court heard.