Police were called to Sevenoaks Road, SE4, at 11.16am on Saturday, 21 October to reports of a stabbing.
Officers attended. A teenage boy, believed to be 15, was found with stab wounds.
He was treated at the scene by paramedics from the London Ambulance Service before being taken to the hospital.
His condition has been assessed as non-life-threatening. There have been no arrests.
Enquiries continue.