The event occurred just before 8.10 a.m. today (May 9) on Trafalgar Avenue.
Officers, London Ambulance Service teams, and an air ambulance responded and discovered an injured youngster.
He was transferred to a hospital in south London, where his condition was determined to be non-life threatening.
As police investigations into the circumstances continue, no arrests have been made.
Police were called at 8.08am on Tuesday, 9 May to reports of a stabbing at Trafalgar Avenue, SE15,” a Metropolitan Police spokesperson said.