Cant get my dog to stop nibbling?

I have a 7 month old english staffordshire terrier that is very Huge for his size and weight. He is 85 pounds and is still a pup. I took him in at 3 months old from a guy that a friend of mine knew. He was badly abused and beaten and lived in his own poop. As soon as I saw him I knew I had to take right then and there. He was so scared he just curled up in a ball through the hole drive home. He would run away and hid if he ever see's me pick up a broom or a mop or even just yell at him. Now He Is so Happy and Loves his New Home! He always has a huge smile when he see's me but he nibbles so much? Idk why he dose it, maybe him being exitied but it kinda hurts lol I have little brusings from it. Im just curious if their is away to make him stop or will he grow out of it? My gf and I are expecting a baby in a couple of months and dont want him nibbling all over the baby. He loves people but I just dont want people to say that he bit them when he was just nibbling cause hes excited to see new people.

A Lot of times when puppy's are very little people like to play wrestle with their hand and they puppies face. Well when the puppy gets bigger they think it is still ok. We used to tell everyone at the vet not to wrestle with your puppy with your hand get a toy instead. Everytime she goes to bite your hand or anything tell her no, give her a toy, and walk away from her. Try this for about 2 weeks and see if she gets any better. And everyone in your house is going to have to do it with you so the dog don't get confused. If she bites once, tell her no, give her a toy, and walk away from her for about a minute.