Intensified pain at night?

To be honest, I really had no idea what to name this thread or how to phrase the title so I'll just start talking. Recently, I somehow managed to injure my shoulder/humerous in a ski fall early July, then after mostly healing up re-injured it playing soccer. As to the nature of the injury, it's definitely not a break; I can move it just fine, it just hurts a bit when I lift something. Imagine your upper arm extended out level with your shoulders, but your lower arm bent down at a 90 degree angle to your upper arm, like you're doing the robot. Then, keeping your elbow in place, your hand is forced straight backward, towards whatever's behind you. That hyperextension you'd experience in your upper arm as a result of that movement is how my arm is injured right now. Now on to the problem/abnormality. My arm hurts during the daytime, but not nearly enough to be little more than an annoyance. However, after re-injuring it, I've been waking up at around 3 am every night (3 nights in a row so far), to find that the pain has dramatically increased to the point where I can't move my arm at all without using my other arm to lift it, and getting back to sleep is super hard. The first night it happened, I thought (in my groggy 3am state of mind) that I had broken my arm and just not noticed it until now. That's clearly not the case, but whatever. Every night, the pain stops as I approach the time I get up and is back to its normal level by around 8 am or so. What is going on and why do things like this hurt so much more in the wee hours of the morning? I've noticed this before with other acute injuries (it happened to a lesser degree when I sprained my ankle a little while ago) although never to such a degree. Have you guys experienced anything like this or am I a freak? Any explanations? Thanks, Isak