Police say the two men got into a verbal and physical altercation between the Bridge and New Road in the early evening of Halloween.
The incident took place between 18:30 and 18:45 and police are keen to speak to anyone who witnessed the altercation or any disturbances in the area between these times.
People with information about what happened can contact PC 116 Ormrod at Guernsey Police on 725111 to relay what they saw that evening.
Alternatively, witnesses can call Crimestoppers anonymously on 0800 555 111.