How to take care of a homesick dog?

we just got a white puddle yesterday form some people who had him for six years. they had to give him up because they were moving into apartment that didn't allow dogs. well at first the dog was all happy but now he's sad and whining and i don't know what to do. now i feel bad for the little guy. is there something i can do to cure his home sickness? also he's hiding in dark corners