Hi ! Good evening. I am Dr Shareef answering your query. If I were your doctor, I would advise you to see if the little one was not injuring the part repeatedly while being ambulatory. That way,a lump of organised hematoma in the subcutaneous tissue below the bruise was more likely to form. In case there was no history of any trauma, I would advise you to get his clotting profile tested follwoing consultation and clinical examination by the doctor. I hope this information would help you in discussing with your family physician/treating doctor in further management of your son s 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. I wish your son an early recovery. Dr Shareef.