sudden onset of periodic Warm sensation on the inside of my left foot

Hello All

You guys have always given me good advice so I hope you can help me this time as well!

My problem this time is a bit particular.
I've had a warm sensation on the inside of my left foot for the past week.

It started off happening only about two three times a day. Now it seems to happen much more often. There's no pain, no swelling, no outward manifestation of any kind that something might be amiss. Indeed, the skin remains cool to the touch, no different from other parts of the foot. The warmth is only felt internally.

What could this be...? Will it go away on its own..?! (i hope so!)
Thanks in advance!!

wabbitte