My 4 yr old has had the flu for 8 days. symptoms have subsided. He has had leg pain for 3 days. Today he woke up could not walk at all Almost didn't make it to bathroom. I carried him. He never complains about pain his entire life. now he is having severe pain and this is going on for the last 3 days. It's very specific it is behind his knee cap goes down his calf and ends at his heel. What should I do should I bring him to the doctor I have called Dr. Said flu. But they didn't do flu test done