A teenager needed surgery to his face after being punched in an incident in Melton town centre.
Police are appealing for witnesses to the assault, which took place in Sherrard Street on Friday night.
It is reported to have happened at around 10.30pm when the victim was punched in the face after trying to help when he saw a fight in the street.
The victim went home but sought medical treatment the next day which led to him needing surgery to his jaw.
He has since been discharged from hospital and no other serious injuries have been reported.
Leicestershire Police say an investigation into the incident remains ongoing.
Det Con Rachel Donaghey said: “We are continuing to establish the circumstances of this incident but from our enquiries, we understand the victim was trying to help after seeing a fight and as a result was seriously injured himself.
“We are appealing to anyone who was in the area of Sherrard Street on Friday night -October 4 - to please think back to if you have any information which could assist us?
“Did you see anything in the area or have you heard anything since which could be related to this?
“If you do have any information I urge you to make contact with us.”
Anyone with any information should contact police on 101 quoting incident 19000533593.