Hello Dear. Most probably your daughter might have injured the arm near the shoulder while playing. It may be just a hematoma of muscle. In that case it should subside within a week, with just pain killers and ice pack therapy. Anyways i will let you know few other conditions also which may cause a lump in shoulder. Most lumps and swellings under the skin are harmless and can be left alone. However, a painful lump or swelling that appears suddenly over a day or two may be caused by an injury or infection. It s likely to be an infection if the skin around the lump is red and warm. Your GP can advise you about how to care for this. A lump on the shoulder, back, chest or arm is most likely to be a lipoma or a cyst. A lipoma is a soft, fatty lump that grows under the skin. It s fairly common, harmless and can usually be left alone. When you press a lipoma it should feel soft and doughy to touch. It can range from the size of a pea to a few centimetres across. A cyst is a sac under the skin that contains fluid, usually pus. It can look a bit like a lipoma but is close to the surface of the skin (lipomas are deeper under the skin). Cysts are firm to the touch. A cyst may disappear without treatment or you may need to have it drained. Consult your GP. The doctor may do certain tests to diagnose. If your GP is uncertain, they may recommend that you have an ultrasound scan or a biopsy. Surgery may be needed to remove certain types of lump. You should also see your GP if you have a lump that: -is getting bigger -is painful -feels hard -grows back after it s been removed In this case, your doctor will want to rule out other types of lump, such as a sarcoma (a very rare type of soft tissue cancer). But do not worry. In my opinion your daughter has just a muscle injury which should be fine by a week. Hope i have answered your question. Feel free to contact me if you have any more questions. I ll be glad to help you. All the best With warm regards Dr Sanjay Kini