Training pup Is this the infamous stage?

hi guys n girls. I’m training my puppy everyday and we are doing g good. He’s 17weeks old his names Chester and he’s a staffy. When I’m doing the trading for instance the nose to hand target he’s starting to nibble/nip as he’s getting his reward. Any advise?
I’ve heard they get to a stage of defiance or not wanting to participate anymore haha could this be the start

He probably just likes nibbling and nipping and your hand is fair game! The best thing is to ensure that when tooth touches skin, the fun stops. Though when teaching trading I wouldn't withhold the treat once he's traded, as it's vital he learns that if he gives something up, he gets something better.

If he seems to be showing resistance to trading, he might have had enough for the time being and need time to relax - no one can learn well if they're at all overexcited/tired/whatever. But if he does seem at all protective of what he has, you need to back off with the training a bit, maybe working more with him giving up something really low value in exchange for something much better.

Totally agree with Judy but I have a couple of things to add - first, the difficult stage is usually when they hit adolescence, at about a year old (varies according to breed). Second, dogs don't really do defiance as such. The three main reasons a dog doesn't do what we ask are that they don't understand, the reward isn't great enough, or that you are working against a deep rooted breed trait (for example, the urge to run in huskies means they can be unreliable off lead). With your pup, he might be getting a little bit frustrated at the task if your reward isn't coming fast enough, or if he has just had enough and has decided he wants to play. And remember, playing for pups usually involves mouthing.

One would assume at 17 weeks he has lost some baby teeth with adult ones pushing through, could teething be playing a factor in his new mouthing habit? My boy loves cold carrots out the fridge when he has net teeth pushing through and it's much more soothing for him than fingers

Thanks ever so much guys! I appreciate the advise I have already slightly backed off with training so hopefully this helps. He’s a cracking dog so I’m not worried. When I get paid I’m gona buy him some lovely chicken or turkey and see if this will be tastier for him x Thanks again x