What Causes Warm Sensation Inside My Foot?

HELLO, I WAS JUST WONDERING WHATS GOING ON WITH ME! LATELY IVE BEEN HAVING THIS WORM SENSATION ON THE TOP OF MY LEFT FOOT IT DONT HURT BUT IT HAPPENS ALOT IM GETTIN WORIED. ITS NOT WORM TO THE TOUCH ITS JUST AN INSIDE SENSATION,, I WOULD APPRECIATE IT ALOT IF ANYONE CAN ANSWER MY QUESTION THANKYOU..