my piggie who is roughly 15 weeks old has in the last few days started nipping at my face and neck gently when i have him out on the setee with me. this is usually once he has had his treat and been playing around on the sofa running between me and my partner. it doesnt hurt. he has always been lively and a bit boistrous, but is this puberty kicking in or could it be him being affectionate?