Police were called to the Lordship recreation ground on Lordship Lane, N17, at 2.39pm on Thursday, 24 June. Officers attended after a report of a fight between males armed with knives.
Officers attended. A 19-year-old man was found with a stab injury.
He was treated at the scene before being taken to the hospital.
His condition has been assessed as non-life-threatening.
There have been no arrests. Enquiries are ongoing.