Welcome to Health care magic. 1. Lesion / lump / swelling at the ankle region - probable cause could be ganglion arising from the tendon, joint and nerve sheets. 2.They are normally painless lumps, in inflamed status symptoms might be seen. 3.If its erosive and tenderness on touch, we can think in terms of factorial infection, infection of hair follicle - if lump is big a small incision and drainage might be needed. 4.Generally if you have no history of been in out door experience some insect can think, but home spiders bugs may not give such conditions. 5.You need to get an appointment with your GP let the lesion get examined and then some treatment can be suggested. 6. Mean while as a remedy - do not press, scratch the lesion, maintain local hygiene, keep clean with antiseptic liquid. Good luck. Hope it helps you. Wish you a good health. Anything to ask ? do not hesitate. Thank you.