Is my hamster okay?

I got my hamster yesterday night. At the store he seemed fine, he was running around and climbing all over the place. I brought him home and now he's acting very reserved. All he does is sit on the his running wheel, occasionally running. Or he sleeps. I am scared something might be wrong. Or is he just scared?

He is nervous about his new surroundings. Just leave him alone for awhile and he'll adjust.
   
You probably brought him home in a box and then plopped him in his new cage, which was frightening for him (although necessary, you did nothing wrong), and he needs time to get used to his new home.
   
I know how exciting it is to get a new pet and how disappointing it is when that pet doesn't rush to you for cuddles but please try to resist the urge to constantly handle him or interact with him.
   
Let him get used to everything and he will start to come to you when he's ready, on his own terms.
   

He's very sweet though... Doesn't bite and he takes treats from my hand. But I woke up this morning around 9:00 and he was still awake just sitting on the wheel. I came back to check up on him at 11:00 and he was still sitting there on the wheel, wide awake. I've ha other hamsters before and they adapted right away and were running around and enjoying themselves the very first day. So I really don't know of he's scared or sick.