Emergency services were called to Nuns Way in Cambridge at about 1.30pm yesterday (Wednesday 19th) with reports of violence.
Officers attended the scene but the victim had left and detectives are keen to trace him.
Last night police arrested a 15-year-old boy in connection with the incident. He remains in custody at Parkside Police Station.
Anyone who saw what happened or knows more about the potential victim of the assault should call police on 101, or online quoting incident 244 of 19 April, or Crimestoppers, anonymously, on 0800 555111.
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