this kind of pain can be due to plantarfascitis(a condition in which heel becomes painful specially when you start walking after long resting period) or it can be due to strain or sprain(ligament/muscle stretch).
Next Steps
Go to a physiotherapist and take the treament.Ultrasonic therapy helps in decreasing the pain and healing of plantarfascia or muscle inflamed,Wax therapy increases blood circulation and helps in relieving pain,stretching will increase the range of motion and relaxation.Exercises will increase the muscle strength.Do it for at least 2 weeks.You will get the relief for sure.
Health Tips
At home do a contrast bath of lukewarm water& normal water(dip the foot alternatively),Avoid hanging of leg for a long time to avoid swelling,do frequent ankle and toe movements.Avoid cold exposure,no long walk, no standing for long period......Take care&Get well soon!