The 17-year-old was attacked in Carlton Road, Walthamstow at 12.35pm on Sunday, November 19.
He was taken to hospital by ambulance and his condition is not life-threatening.
Police in Waltham Forest have issued a Section 60 order which allows them to stop and search people for weapons.
There have been no arrests and enquiries continue.An 18-year-old man was left in a critical condition when he was stabbed in the stomach in Mount Pleasant Road, Walthamstow on Thursday, November 16.
wo days earlier an 18-year-old man was stabbed as he ordered a sandwich in Subway in St James Street, Walthamstow on Tuesday, November 14.
Anyone with information is asked to contact Waltham Forest Police on 101 or call the independent charity Crimestoppers anonymously on 0800 555 111.