U must get one X ray done of the area lateral and AP view. Swelling can be a ganglion - protrusion of joint sheath at elbow joint which is self limiting , just provide some rest to the area. other possibility is it can be a Tennis Elbow. Tennis elbow is caused by either abrupt or subtle injury of the muscle and tendon area around the outside of the elbow. Tennis elbow specifically involves the area where the muscles and tendons of the forearm attach to the outside bony area (called the lateral epicondyle) of the elbow. Another common term, golfer s elbow, refers to the same process occurring on the inside of the elbow ,called medial epicondylitis. .Overuse injury can also affect the back or posterior part of the elbow as well.