Hi. Thanks for your query and an elucidate history. This can be due to inflamed lymph node in the abdomen, I would think of diverticular disease. The best way is to get the standing X-ray of the abdomen and high resolution ultrasonography. Consultation with a Doctor can help to get a clinical diagnosis based on actual physical findings likes rebound tenderness, tinkling on auscultation, site and severity of tenderness and so on. Further tests and diagnosis will be based on these findings. so better to see a Doctor and get investigated to go for further treatment. You have already undergone appendectomy so you can understand the importance.