Hi ! Good evening. I am Dr Shareef answering your query. Although a personal physical examination of the lump would be helpful in reaching a nearby diagnosis, most probably with a history of trauma, it could be an organised hematoma on the left side of your back. To confirm the diagnosis, if I were your doctor, I would go for an FNAC (fine needle aspiration cytology) followed possibly by an excision biopsy depending on the report of the FNAC. Considering the duration of more than 4 years, clinically it might be a benign lesion not to worry about. However, for cosmetic reasons it might be required to be taken out.Therefore, I would advise you to consult a general surgeon and get your self assessed for the same. I hope this information would help you in discussing with your family physician/treating doctor in further management of your problem. Please do not hesitate to ask in case of any further doubts. Thanks for choosing health care magic to clear doubts on your health problems. Wishing you an early recovery. Dr Shareef.