Last night, I had my first real injury from doing BJJ; I dislocated my left shoulder. We were rolling, I was on my back, my opponent in half-guard, I had an underhook on the half-guard side and I was moving to take his back. Basics. Then he underhooked my other arm, pulled it up -- and here is where it gets a little foggy -- I think he tried to do a weird modified straight armbar, where he put my hand on his shoulder and tried to press against the elbow of my outstretched arm. A little confusing -- also for me -- but the end result is that I felt something pop in my shoulder and a shooting pain ran along my arm. I hadn't tapped yet, but he felt my arm go limp so he put me on my back again, at which point I decided to tap. He got off me and asked me if I was okay, and I couldn't move my arm anymore. I looked at my shoulder and saw that it was a few centimeters lower than it should be. My teacher came up and before I could protest popped my arm back in. That hurt more than it popping out. I iced it for the remainder of the class and inspected it to find no bruising or swelling. I took a painkiller and that was that.
Today I woke up and I found I had a lot more mobility in my shoulder. I can even left my arm a bit again. I don't think it will take long for this to be healed, but still it sucks.