It can be due to plantarfascitis which occurs due to inflammation in the cushion like structure present in the heel. Pain usually occurs when you start walking after a long rest like sitting /lying and decreases after some walk /movement .
Next Steps
Go to a physiotherapist.. Ultrasonic therapy +wax therapy +some stretching exercises will be helpful for sure.
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no hanging of legs+use heel cushions +use soft footwears +do ankle movements at ever 2 hours intervals /after a long rest+no cold exposure +avoid walking on hard surface .