It's entirely normal for dogs new in a home to be unsure, even a bit reserved. The pup has no idea what your intentions are, what are the rules, where IS my 'bathroom' area, is he safe here, etc etc.
Time passing and LOTS OF TEENY TINY TREATS delivered from your hand, or have pup lick tiny dab of peanut butter off of your hand, is very very bonding to the dog. Try your best not to reward signs of fear or distress with affection. (this is harder to do than to say, i know, haha!!)
If you brand new housemate is too timid to take treat (i keep all treats TINY, and i use crumbs of real meat) directly from your hand, then settle for tossing treats to pup, and toss them in ever shortening distances so pup must come closer each time to get treat.
Be aware, too, that you know this pup is yours, but, he doesn't know this just yet. So far as the pup knows, he is lost, and you are just some friendly stranger so far.
lots and lots of tiny bits of real meat, hand delivered, helps pup bond with you.
CONGRADULA I clean up and then spray with an enzyme cleaner. TIONS AND GOOD LUCK!! SEE YOU AROUND!!!