I Have Started Having What Feels Like Muscle Pain In

I have started having what feels like muscle pain in a small spot just under my ribcage on my right side. It onl happens at night and when I sleep on that side. Sometimes I can feel it vaguely during the day but it is barely noticeable. I have been working out lately but not excessively so and have never had this particular type of pain before. It began about two weeks ago.