hello i am a 15 year old male and i have a lump on the back of my lower leg under my knee. it is verry stiff around the area and it is about 3 inches in diameter in the center it is red and that is about 1 inch in diameter and at the very center there is a small black scar it looks like. it is very swollen around this entire area and is starting to hurt slightly when i walk. i am just concerned because i hve had this for about a week and it has gotten bigger and has hurt more. i have a doctors appointment in the few days but i am just wondering if their is a need for immidiate concern. thank you