Pain in upper right arm?

So, for the past 3 days or so, I've had this strange pain in the inner part of my upper arm. It comes and goes, but seems to worsen at night or when I lay down. It has started to bother me at work as well. It doesn't hurt more when I put pressure on it, or when I move my arm in a certain position. Obviously, I plan on making a doctor's appointment, but does anyone have any ideas on what this is or how to alleviate some of the pain in the meantime? Thanks!