Swollen Lymph node in leg/groin area. What could it mean?

I just got back from the doctor. They ran all kinds of test ranging from STD check up and lupus. My white blood cell count is normal (around 6 x 10^6) and everything else is normal. I have a followup next Tuesday, but I'm really worried what it is. I dont know which lymph node it is exactly, but its on the left leg about 6 inches down and 6 inches left... Please help.