T.H.
Well have you gotten new shoes recently? Everydone does walk differently using different parts of their feet in different ways, so if that area is where you put a lot of pressure then it could have just worn out your shoe in that area and it's time for new ones.
I would suggest going to a shoe store that will test your foot and give you orthotics if necessary. My husband and a few others I know have had to do this (and shoot, I probably should too, just haven't done it yet) and it's made a world of difference. You can still get normal shoes there and they carry a variety of running/walking shoe brands. It is a bit more expensive but I think it'd be worth it if you have recurring problems.