I too have this,,about every 2-3 months,,It is one spot,,I take a platic skewer and remove it,,Same place as you said,, it is gross but it smell pretty bad. A doctor said it was a pearl. I am now trying to find out more info. Some times it will dis lodge during activity and I spit it out ,,its small like a bb. This last time it was way bigger. It is not puss from infection(I think). Its alway in the same spot.