Sounds like fat cyst
Sometimes sweat gland can grow inwards producing a cyst.
If this bothers U, can be removed. The cyst has capsule around it which also needs removed and leaves indentation which dissapears slowly. If it begins to smell or leak U can have removed w insur claiming infected, Otherwise ins may not pay. Also they can recur. Show primary MD & seek derm to examine. Removal not a big deal.