Out of all the dragons I've had, Greta is the only one who was a pistol from the start. She would literally LUNGE at me with her mouth wide open whenever I opened her cage. She was a nasty little bugger. I personally thought it gave her personality LOL.
I would highly recommend getting some THICK gardening gloves and putting them on...and just picking the dragon up. Let them bite the glove, let them see it doesn't hurt us. He'll get over it. If it's a baby, it really doesn't hurt. I just personally like the gloves because they can bite at it all they want. I shoved a towel, glove, or even some greens in Greta's mouth every time she tried to go after me. She's the sweetest thing now. Sometimes it just takes some time, especially if they haven't been handled much as babies.