Police were called to Sunnyside Road shortly before 3pm yesterday (October 25).
Officers arrived but could not initially find any casualties at the scene.
However, they were later called by medical staff to a 22-year-old man who had taken himself to hospital.
His injuries are being treated as life-changing but not life-threatening.
A 15-year-old boy has been arrested on suspicion of attempted murder and is in custody.
Police continue to appeal to the public for any information on the incident.
A Met Police spokesperson said: “We understand the concern this has caused the local community and residents can expect to see an increased police presence in the area.
“Enquiries continue and anyone with information that may assist police is asked to call 101 quoting CAD 4199/25OCT25.”
