Hi, I Am A 45 Year Old Male In Good

Hi, I am a 45 year old male in good physical condition. I had a severely perforated appendix that had to be removed (peritonitis surgery, I was told) which was done successfully exactly 5 months ago. I am healthy since then, but there is a large lump in my lower right abdomen which did not go away. It is on the right side of my surgical scar, and it sticks out when I stand up. My doctor had told me that it would go away in 6 months, but after the 5th month, it did not get smaller, not even an inch. I am freaking out right now. It doesn't cause pain or anything, but it is there as big as day one. What is this? Thanks in advance.