Hi, thanks for sharing your health concerns with HCM! If I were your treating Doctor for this case of LOWER BACK lump, I would come up with one possibility that is some infection But concurrent viral infection also should be excluded! However, the mode of infection could be some mild penetrating injury, insect bites, folliculitis or small boil! You might need some antibiotics and cold compress in the region for temporary relief! Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you good health.