The dragons I'm familiar with are omnivorous, but they vastly prefer meat. Cubed pieces of elk or cow steak, or some fish filet, would be wonderful for the little one, along with a little rice and some orange slices for other nutrients. If you can convince it to eat veggies, it would be good for it, but like most children, I doubt it will want anything to do with them for a while.

[He takes a couple steps closer, finally scanning the dragon to check its teeth, vitals, and gender.]

It's going to be a little antsy until it eats, then it's likely to sleep for a while. Young dragons burn a LOT of energy while their metabolism sorts itself out.