He is in a whole new world and needs to get used to the surroundings, Cage and People. Just let him sleep peacefully and have everyone around him stay calm, talk gently and happily to him.
Since he picked you at the store, approach the Cage slowly and see if he offers to beak you again. Then depending on his reaction, either offer to open the cage and see if he will step-up or just back away a little, sit next to the cage and talk to him.
Patience is the main ingredient right now. :-)