Aggressive growling and mouthing

My staffy is now 17 months old and on the whole is the most loving affectionate friendly dog you could ask for, loves people and is great with other dogs. The problem i have got now though is that on a few occasions he has growled and mouthed quite aggressively at me when I have gone to correct him and move him by his collar. This has happened a couple of times for example when he has gone to urinate in a relatives house and i have shouted "no" and gone to move him outside by his collar. When it's happened I have put him outside on his own and after 10 minutes when I go out to him he is very sheepish and knows he has been naughty. I will stress he has never actually tried to bite or nip me but is just very vocal.

My question is, is this a common phase that will pass or is this something that needs addressing before it grows into a bigger problem ?

I will add that he is an intact male and i really planned for him to stay that way as other than this minor issue he is the perfect dog.

Any advice appreciated thanks.

He's pushing the boundaries & letting you know it!

I wouldn't be too concerned as long as all it is is mouthing off! However, I'd correct him when he does it - a sharp "No!" and then ignore him for a few minutes. He'll soon get the hint. You could also try distraction - keep a few treats in your pocket and when he growls give him something else to do; sit, down, paw etc & then give him a treat.

It isn't because he's entire, he's just growing up & flexing his muscles! Once he realises that you won't accept the behaviour it'll stop.

I think its just sticking to firm no and sticking to your guns. He maybe trying to challenge you as to see how far he can go. My Vinnie does it from time to time and is now 20 months old. If he is good with people and other dogs in general I would say nothing to bad to worry about.

Thanks for the responses. I thought that was probably the case if I'm honest but it never hurts to hear some reassurance does it

As well as pushing the boundaries, he might not like being held by the collar. Loki does the same with me if I try to move him by his collar (only ever when he's in a mischievous mood), no actual biting, just a bit of defiance and stubbornness. Agree with what's been said in telling him 'no' and ignoring him for a while, but it doesn't sound too bad, he's still young and rebellious