You might want to see your doctor about this. Any pain that significantly interferes with your daily activities, is not improving after a few days, or worsens, should be checked out by a medical professional.
I cant say for sure what is wrong I just wanted to say you may want to check into cubital tunnel syndrome .I have the same symptoms as you and was recently diagnosed with it .Cubital tunnel syndrome means your ulnar nerve in your arm is trapped at the elbow .You really should be checked by your Dr but this may be something you might want to mention to him .I wish you all the best and I hope you are able to find out what's going on
It could also be lateral epicondylitis, also known as tennis elbow. You don't have to play tennis, overuse of the elbow joint can cause it. Either way, you need to get it checked out so that you don't inadvertently make it worse.