Depending on your country call a vet or a licensed Wildlife Rehabilitator.
They will be able to tell you what to do and where to bring the animal.
Taking care of a wild bird is not simple and needs experience which Wildlife Centres for example have. They will raise the bird and release it back into the wild.
Depending on your location (if you add that I ...
He needs food mashed to semi-liquid mush and put in his mouth. A pet shop may have prepared food for infant parrots. A pigeon would need grains and corn, not vegetables. I once had a crow about that age; his favorite food was earthworms (cut into pieces and put into his mouth, at first).