Officers investigating a report of assault in Manor Road, Desford, are asking for anyone who witnessed the incident to come forward.
It happened between 9pm and 9.45pm on Sunday 19 May.
The victim, a 14-year-old boy, was punched by a man, causing a cut to his cheek.
As part of their enquiries, police are now appealing for anyone who was in the area at the time but has not yet come forward to do so.
PC Hayleigh Taverner, the investigating officer, said: “I would like to speak to anyone who saw what happened that evening but has not contacted police.
“Cast your mind back. Were you in Manor Road on that Sunday evening? Did you see what happened or do you know who was involved?
“Any information you have, no matter how insignificant you think it could be, could help with my investigation.
Call 101, quoting crime reference 19*256535.