My girlfriend and I just adopted a 15 week old German Shepherd/Blue Heeler mix. He's very intelligent and does very well with basic commands (sit, lay, and stay). We noticed he's been nipping more and more. It's nothing aggressive. Usually playing petting gradually turns into a lot of nipping (especially after walks). Mid kiss on my nose usually turns into a bite at my nose. He is 15 weeks old so I'm guessing this isn't strange. Is there anything we could do to prevent this? Thanks in advance!