My Shoulder Hurts

My left shoulder, to be precise. I am right-handed, so I am a little confused as to how this happened. No, that is total denial. This is a knitting-related injury. On Christmases past, I have had achy forearms (bad!), but this shoulder thing is new. I don't think that I've been knitting any more than usual lately, or anything unusual. I am still working on the Central Park Hoodie in Ultra Alpaca for my grandmother. The yarn isn't hard to knit, but I am using some old-school, heavy, metal needles instead of my usual Addis/HiyaHiyas/Harmonys. Could they be to blame? Could this be from using my laptop too much or sleeping in weird positions? I need a day off from all of this.
Do you think I could work on a sock while this heals up?
Probably not. Sigh.
Tomorrow, I think I will go see a movie at the place in Indiana with cheap matinees of new releases. I can get some (relatively) cheap gas while I'm there. I'll be able to eat greasy movie theater popcorn without having to worry about getting the "butter" on my precioussssssss yarn. This plan gets better and better...
I am slowly working my way through World On Fire, a book about the British involvement and influence in the American Civil War. It was written by the historian who wrote that fabulous Duchess of Devonshire biography a few years ago. This is a bit slower moving, as there are so many characters (historical figures) to keep track of, what with the Federals and their British supporters and the Confederates and their British supporters. Still, very interesting. I had no idea what a dick Seward was before reading this book! The other reason this hasn't kept me riveted, I suspect, is my extremely limited interest in the American Civil War. It was long, it was awful, and afterward people said "the United States is.." instead of "the United States are..". It's the stuff of 5th grade reports, reenactors' weekends, and sad folk ballads. I'm midway through 1863 right now. Will write more once I've finished the book.