Give him seeds everyday. Keep some in front of him and see what happens. All other food items should be fed through syringe. Holding the syringe in your right hand, put the syringe in the baby's beak angling it from your right to left, the baby's left to right. Give a little squirt of formula, the baby should chirp and bob his head up and down. Repeat this until you feel the baby has had enough. You do this by feeling the crop.
Give him some time keep some millet in front of him after few more days.