Yes I agree with robin sounds like a cyst I had one on the sole of my foot and the palm of my hand I read that if you massage them regularly they diminish, so I did and yes they went away ..takes w hile but just massage the area a few times a day ..see if it works , you may also be able to get it removed .good luck
Prob a cyst I have ton of those some I took out surgical and some are just there I would just have it checked out mine get huge like a size of a dollar coin sometimes they just disappear