Go straight to a podiatrist, do not pass go. I would go to a local running store (not big box sports store) to ask for recommendations of good docs. If this is in fact a flaring up of the plantar fascia ligament:
if left untreated it can lead to heel spurs. If you thought you were in pain
now... My father had lifelong battles with this in both feet, to the point of getting spurs.
Make an appointment NOW.