The incident happened at 4.45pm between the junctions with Kirby Road and Beler Way and led to the road being closed to traffic for more than four hours.
An ambulance crew attended the scene and took the child to hospital.
A Leicestershire Police spokeswoman said: “Shortly after 4.45pm yesterday a report was received that a child had fallen from a car travelling on the A607 in Melton Mowbray.
“The road was closed while both officers and colleagues from the East Midlands Ambulance Service attended.
“The child was taken to hospital to be treated for minor injuries.
“Enquiries to establish how he fell from the car are continuing.”