Help!What is this circle on my foot?

hi, I apologize, I submitted a message earlier by accident.. I wasn’t finished explaining my situation! I was explaining that I have a small circlular something about 2 inches below my ankle on the heel of my foot. It is smooth and about the size of the tip of my pinkie. It feels deep but doesn’t hurt and is barely visible. I was out of town and ran out of socks, so I jogged w/no socks. Also I walk barefoot quite often outside. I have never had a corn,bunion,wart..but ocassionaly will have a small water blister. I don’t have much insurance coverage so am looking for any over the counter solutions! Can you tell what is on my foot through my description?
Thank you for your time. I really appreciate you help!Monika