I have pain in my shoulder with a knot on top of my shoulder bone?

Ac joint??: Is at the top of the shoulder and problems can cause shoulder pain. Or might be spasm of overlying muscles. A physical examination should help sort this out or if still remains unclear the dr can arrange tests.

Could be inflamation: Sprain/Strain of your AC joint ( acromioclavicular).Sprain can last up to 6 weeks. Don't do anything that makes it hurt worse,Advil like drugs help,ice for 15-20 minutes 4-6xa day. See doc ( Orthopedist) if persists or to confirm diagnosis.