My 7 years old son has got amblyopia or lazy eye(left).how can he get normal?

You are lucky: He is still young enough for treatment. Take him asap to see a pediatric ophthalmologist. If you don't, he will have a blind eye forever.

Rx May help: Ambliopia is the process where the brain ignores the "camera" picture from one eye because it is less clear or causes double vision. It can sometimes be improved if the weaker eye is strengthened (glasses), the stronger eye is patched or if the eye is lined up better with surgery. If the process has gone on too long, the brain ignores the fix & surgery is simply cosmetic.