You are getting this pain from daily activities? Just walking around, holding onto something, etc? Go to your doctor and find out what is up and ask him to refer you to a physical therapist to start therapy if he can identify what exactly was injured. "Sprained rib muscle" doesn't do much to describe where the pain is located and identifying what needs to be done. I'm not sure why you haven't done anything about it since then, if the pain is spreading from your upper back and causing numbness in your pinky.

By your upper right back, you mean the trapezius correct? I'd assume this muscle because you were doing shrugs, but what part of that? Next to your neck, on your collar bone area, or more towards the back where your scapula (shoulder blade), or your deltoids? I'm asking this because I was wondering if you sprained one of the few ligaments involved with movement of your shoulder.

Either way, GO to a doctor and tell him about this, then let us know what happened.