Pain in the deltoid area?

I’ve been having arm pain in what seems to be the deltoid muscle. What can possibly cause this?

My pain is not above the shoulder though (but still where the highlighted area is), its more on the side of my arm, I guess between the biceps and triceps.

Also, I should probably note that while I’ve iced and rested the arm, I still have pain about 2 weeks since I first noticed it.