The assault, which is being treated as ‘Grave and Criminal’, took place around 23:30 in Hot Stuff Pizza, St. Helier.
The perpetrator was then said to have ran from the Stopford Road premises in the direction of David Place.
Pictured: Hot Stuff Pizza, where the headbutt occurred. (Google Maps)
Those with information are asked to contact Police on 612612 or make an anonymous report via Crimestoppers on 0800 555111.