GoldenCharm...your pup looks so adorable...but I know pictures don't show the teeth he has

My Lucky was so nippy...all the time...that I myself (and this maybe just me) was unable to bond with him till he was about 13-14 weeks. I'd never had such a nippy pup...and never had to deal with bloody arms.
But this is my opinion based on articles I've read and my own experience. A playbiting pup is a pup who will learn an expesially soft and sensitive mouth. A non-playbiting pup will not have experience in mouth control and thus will bite harder and be more dangerous as an adult if surprised or irritated. So, in my opinion you don't want to make him stop all mouthing.
I would use this time to train the mouthing...letting him know what hurts and giving him consequences for it...like timeout or ignoring him when he wants to chew some more. I wouldn't try to make him stop...but work on getting him to control it. In time he should mouth and stop mouthing on command.
I think...that because Golden Retrievers are more mouthy and bite-happy as pups then some other breeds...this is one of the reasons they are considered soft-mouthed and gentle as adults.
I'll let some others give you specific techiques to help control this. I just wanted to give you my opinion on how this behaviour is actually a benefit later as an older pup and adult dog.