My husband has had random transient warmth and swelling in different parts of his legs for years. We just chalk it up to various spots of inflammation for various reasons. It comes and then goes.
Since you are young, in good health and not at risk for a blood clot, I would not be concerned in that regards, but if you continue to have the issue, it gets worse, or if you simply can't let go of the worry regarding it...then making an appointment to talk with your doctor would be a good next step.
Try some coping skills first though and give it some more time. I am betting that in a day or so, it will be gone.
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT