Officers attended at the scene at Rawson Street North, Boothtown, this afternoon.
The three storey block of flats are situated by a playing field and near Akroydon Primary School.
Paramedics were first on the scene and alerted police at 2.22pm (Thursday, November 2).
A 16-year-old boy was discovered with a leg injury, which was thought to be a stab wound
He has been taken to hospital with injuries which are not believed to be life threatening
A man has been arrested in connection with the incident and is currently being held in police custody.