Hi ! Good afternoon. I am Dr Shareef answering your query. Although it needs to be examined physically before opining on the lesion, with the history, it seems that your shin has been hurt somewhere might be without your knowledge, or an event which you do not remember now. This possibly resulted in a hematoma formation(collection of blood in a closed space) which gave rise to your present symptoms. This should get absorbed in due course. However, it would need some specialist opinion in case of any super added infection resulting in an abscess formation. As the duration is already of 4 weeks, I would rather suggest you to get it examined by a general surgeon for further management. Till then, you could go for an anti inflammatory drug along with a proton pump inhibitor. 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.