How do I know If I pinched a nerve in my back?

I've been lifting heavy objects during the past week, like boxes full of stuff for a theatre show I'm working on. Not very heavy, but more than I usually carry. I usually have a heavy backpack and I'm wondering if it's possible that all this weight could have cause me to pinch a nerve in my back. In between my shoulder blades just before my left shoulder blade starts there a area that tingles, not numb exactly but an annoying tingling sensation that I've felt there, on and off for the most part for the past 5 days or so. Could this be a pinched nerve? It doesn't hurt but it's annoying and hasn't gotten better yet. I didn't have one moment where I was in pain and I knew I did something to my back, it just started tingling. Do pinched nerves usually go away on their own? Or is this a sprain of some sort? An answer would be great, I'm a big worried! Thanks!