I woke up with a stiff neck and shoulder muscle. my worry is why it was swollen up? is that normal??

Shoulder pain: Clearly this is not "normal". You have injured yourself somehow. Perhaps you were lifting something that was too heavy for you ar you repeatedly exerted yourself to 100% with the shoulder and have and overuse problem. Ice it 20 minutes 4xday, take some anti-inflammatory (ibuprofen 600mg 4x day) and rest it. If its not better in a week OR it gets worse (Red/hot/more painful) see a doc.