Hello, There might not be any broken needle in your arm because the latest disposable needles are not so fragile and she could take the needle out and checked the tip. So please relax. The causes of bump on arm may be hematoma or punctured vein, allergic reaction at the injection site, or post injection inflammation. Treatment depends on the cause and how bad the reaction is. Most post-injection inflammation is mild. It goes away on its own in hours to days. If treatment is needed, it may include cold packs. These help reduce swelling, and pain. Over-the-counter pain medicines. These help reduce pain and inflammation like Ibuprofen, Acetaminophen. Thus, the bump will go in few days. Even by using above treatment for a week, the bump persists or increases in size, then you can consult a physician. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Pallavi M., Anesthesiologist