This is plantarfascitis, an inflammation of a cushion type structure in the heel, pain increases generally when you walk after a long rest. And after sometimes it remains even at rest.
Next Steps
Go to a physiotherapist.. Ultrasonic therapy for reducinf inflammation and pain and for the healing+Paraffin wax therapy for increase in blood circulation +some stretching exercise will help for sure... For 2-3 weeks.
Health Tips
At home- hot water fomentation, frequent ankle movements before you start walking... Get well soon!