My arm has been sore for a few weeks, at the elbow, both inside and outside. The whole arm feels weak, like I’ve been writing for ages using that arm but I haven’t. Can’t bend or straighten it easily or use it to pick things up as it’s painful. I was trying to think what could’ve caused it but all I can think of is that I had a blood test just before it started. She struggled to do it there and used the other arm and left a big bruise. (On the other arm) What could it be? Should I talk to a doctor or just see if it goes on its own?