A hard material on the heel hurts me. What is the cause?

The heel counter, the resin material built into the heel, may be deformed.
The heel has a built-in heel counter that plays an essential role as a protective function. But the heel counter will be deformed if you repeatedly step on the heel.
Please note that once deformed, the heel counter may not be restored, and the fabric inside the shoes may be torn, or the feet may be damaged.