Hello. my arm has been hurting, behind where they do blood tests. it feels like it's a joint but i'm not sure. sometimes it just hurts, then sometimes?

Blood Test Done: If you just had a blood draw from that area it isn't uncommon for it to hurt a few hours after the blood draw. Give it some time. See you doctor if it continues.

Pain in elbow area: Did you, I fact, just have blood drawn? Sometimes the needle does cause some injury to the soft tissues which may bother you for a week or so. If no blood tests recently, it is probably an orthopedic issue such as a tendinitis or a host of other musculoskeletal-skeletal afflictions. Which an orthopedist can evaluate. A joint issue may be in play, but better for a Rheumatologist to evaluate it.