Hi, Thank you for your query. I can understand your concerns. It seems that you are having Olecranon bursitis which is an inflammation of olecranon bursa (small sacs of fluid that help joints move smoothly) at the back of the elbow . The swelling or lump is caused by increased fluid within the bursa and is tender with movement or when touched.Mild but repeated injury (direct or indirect-as in tour case ) is thought to be the common cause. It often clears on its own. Treatment may be needed in some cases to reduce the inflammation and clear any build-up of fluid. You may find the swelling improves with (R)est, (I)ce packs, (C)ompression (wearing a bandage) and (E)levation (keeping the elbow in a raised position). Avoid leaning on your elbows, protecting your elbows during sports activities with elbow pads (in future), and use nonsteroidal anti-inflammatory drugs(NSAIDs) to relieve swelling and pain. Treatment for sudden (acute) bursitis may include drainage of excess fluid in the sac with a needle. Regards Dr. T.K. Biswas M.D. Mumbai