Question: I woke up Sunday morning with lower leg pain that caused me to limp slightly, it was above the right ankle and in the lower inside shin area and really tender to touch. I exercise regularly, and I had increased my cardio significantly several days before. Now, as the day went on it eased off but sometime after lunch I started feeling weird. I got to my home about 2:30 in the afternoon and started chilling and feeling feverish. For the next 6–7 hours my fever got up to 101.9 and I had real shaking chills. I Took two Tylenol 4 hours apart during the time of fever and 2 more again about 3am. I broke the fever and chills and approximately 9:30 PM that night and my temperature stayed down from that point on. Don't know if the lower leg pain/injury and the fever and chills starting are related or not related. Temperature was normal when I got up the next morning and I felt fine except for a little bit of light headedness, I figured was it just from the fever hangover. About two hours later, I got in the shower feeling pretty much back to normal when I noticed I had a swelling and redness in my right groin/hip flexor area. It is swollen fairly large, puffy, red and tender in the upper area towards the hip flexor insertion. Also, there is no pain to lift my leg or knee upwards as would be with the hip flexor injury. Also, I do not have a cat and have not been scratched anytime recently.
A quick history from me, underwent radical robotic prostatectomy last March 2015. Post surgery test showed that the cancer was removed successfully no signs of any cancer cells in the margins of the removed prostate or in the lymph nodes that were removed. I have had three blood test, the last one two weeks ago, that all showed undetectable PSA. I feel good, I'm healthy,strong and eat good nutrition and exercise regularly, weights and cardio. I am 6'6" and weigh 225 pounds, my waist size is 35 1/2.

What could this possibly be a symptom of?