what kind of shoulder injury is this(not rotator)

[bigdog123]

I woke up last Saturday and my shoulder felt funny. It's near the rear deltoid region. But I have been training long enough to at least know that it isn't a rotator cuff injury.

I mean you can touch the muscle without even pressing hard and feel the tender spot. It's kinda dull and feels like scotch tape is over part of the muscle if you get what I mean. Kinda of like a minor tight feeling.

It's weird because it didn't even happen while I was training. I first felt it when I woke up on my off day. I may have slept on that shoulder and aggravated it I don't know. Thanks for any advice you can give!