Anyone with a dog?

Okay so we have a Pitbull he’s a little over a year.

We rescued him as a puppy and he was maybe 5 weeks so we’re all he’s ever really known.

When he was a puppy he was so independent, if someone walked in, he didn’t even care to look at, he’d just stay to himself doing whatever.

Now if someone comes in he HAS to get their attention or he’ll go crazy, if he’s in his cage he’ll start crying. He doesn’t really bark but he does cry.

He never had an issue with biting but the other day our friend came over and he was talking to my fiancé and not giving our dog attention and he put his whole hand in his mouth and bit it... it’s NEVER happened before and I DONT want it happening ever again... he’s always around kids and he doesn’t behave this way around little humans and I have a 3 month old.. but lately he hasn’t been caring about little kids being around, he’ll bump into them and try to jump on them... where did my puppy go 😭 he’s been trained all his life. He knows about 30 commands. He always needs to follow people and doesn’t listen for long anymore. I’ll tell him to lay down and stay and it’s takes me saying it over and over again and when i leave the room it’s like he doesn’t care. He’ll go right back to doing it. Anyone have any advice?