Thank you for asking your question. My name is Dr Marcucci and I will try to help you out with your question. This lump could be a number of differ things but from what you explained it sounds like it could be a deeper contusion or an abscess, or a foreign object like a piece or part of the hip replacement components. Deeper contusion is related to the trauma you recently had and in the healing process the visible swelling and bruising has healed but the remaining deeper contusion often remains longer and heals at a much slower rate. You can ice this area. An abscess can form from an infectious process. this occurs when the body recognizes some infection or a foreign material in the body. The defense system in our body works quickly to wall the area off to prevent it from spreading to the rest of the body and once walled of an abscess can form and pus develops within the abscess. the treatment for abscess often include an incision and draining the pus and often requires antibiotics as well. If a piece or a part of the hip replacement became loose or broke off you could also suffer the symptoms you mentioned. if this is the case you would need to see a doctor for X-rays and then possible removal of the piece or part and repair of the hip replacement. Hopefully this information helps you with your situation. Ultimately you may require further investigation by a physician that examines you in person. Thanks again for your question and be well and healthy. sincerely, Dr. Jared Marcucci MD