Police officers were called to the junction of Prince Regent Lane and Barking Road.
The 12-year-old was taken to a hospital for a check up.
His injuries are not believed to be life threatening or life changing.
A London Ambulance Service spokeswoman said: ““We were called at 2:55pm to Prince Regent Lane at the junction of Barking Road to reports of a road traffic collision.
“We sent an ambulance crew to the scene who arrived in under three minutes.
“We treated a child for head injuries and took them to a major trauma centre as a priority.”
Prince Regent Lane is now reopened after being closed in both directions.
Claire Mann, TfL’s director of bus operations, said: “We are sorry to learn of an incident involving a route 147 and a child on Prince Regent Lane and our thoughts are with them and their family.
First video is where he is riding his bike
Second video is where the child is hit by a bus