If your puppy is now only 8 weeks old, I would think you haven't had him very long. So he probably hasn't learnt what the command "NO" means, you need to teach him. If you find that too difficult to do after a good time, then like others said you need to reward good behaviour and ignore/correct bad behaviour. He's very young and everything is fun and new to him. He's just exploring and experimenting, even if you do find it annoying wrong.