Thank you for good resolution photos. This could be a corn / callosity due to chronic pressure or irritation from the footwear. However, this could even possibly be a plantar wart. For now You can use salicylic acid ointment -12% over the area daily at night and vaseline jelly in the morning. ideally you should visit a qualified dermatologist and get it pared and treated.
Next Steps
see a qualified dermatologist near you