What is the ruling regarding the many prayers performed previously while there was dirt in the cracks of the heel of the foot, without washing it completely due to ignorance of the ruling, and must these prayers be repeated?

Some scholars are of the opinion that a slight barrier does not prevent the validity of purification (taharah), and according to this view, nothing is required of you. However, according to the majority opinion, if you are in doubt about the existence of a barrier, the default is that it does not exist. Doubt concerning an act of worship after completing it does not affect its validity. But if you are absolutely certain that you did not wash what was obligatory to wash due to your ignorance of the ruling, then there is a difference of opinion regarding the obligation to repeat those prayers. You may act upon the opinion of those who do not obligate repeating them. However, if you wish to be cautious and make up those prayers, that is good.