circular marks on my hands

I noticed a skin colored, slightly red mark on my left hand about four months ago.  It was raised around the edge and smooth and flat in the middle.  I left it alone and it finally went away for the most part.  It is still a bit noticeable but seems to be going away.  Now, I have a smaller circular mark that looks the same on the other hand.  The raised edge almost looks like scar tissue because it is very smooth.  I do not know what these are and what could be causing this.  If you know what it could be, I am interested to find out.  Thank you for your help.