New here

Hello all,
I’m new to this forum and I’ve decided to join because I’m having behavioral issues with my dog. He will be 2 in January, he is a pit bull mix (not sure what he is mixed with) were thinking gray hound or Dalmatian because of his height and weighs about 80 pounds.
When we got him when he was a puppy, is was very timid and skittish Which I think is why I’m having trouble now.
He likes to jump and use his paws when playing. He can get very nippy still while playing. But my biggest concern is when strangers or someone comes over he is very protective and likes to jump and try to nip. After a while he ends up loving them. Also, when my nephew comes over he likes to nip him and I know being a hyper kid and in his face doesn’t help. But I get nervous for the safety or anyone that comes over and I put him away but I don’t want to have to do that.
Any recommendations or things to do to help him through this? He’s overall great dog, very smart, listens most of the time, and very loyal. We are also expecting baby boy in a short few months and I want to work on his training before the arrival of our son. Thank you again!