“When should you go to the ER for elbow pain?”

If you cannot bend or move your arm, if there is no improvement with over the counter treatment and a few days of rest of if it is getting worse. Ideally you should be seen by your primary care physician so you still get seen and assessed and treated. Look and see what maybe caused the pain, if you rest your elbows on the desk or lean on your elbows it may just be bursitis so stop doing whatever is causing the pain and see if that allows it to heal. Good luck with that bc even I do it it's a hard habit to break!

Most of the time, elbow pain does not warrant an emergency room visit. I would suggest following up with a primary care doctor to be evaluated if the pain persists.

Never. That is something you would need to speak with your orthopedist with.