Greetings, sorry for the pain.
You are having compression of fat pad at heel due to uneven muscle length and strength, you are developing a flat feet or already you are having a flat foot.
Next Steps
Get to see a physio for treatment. in meantime ice the area thrice or twice a day. it will take 2-3 months for you to full recovery.
Health Tips
if any doubts feel free to contact or get online consultation.