Hi and welcome to HCM. thanks for the query.
It look like atheroma
and this is very commonly seen.This is actually subcutaneous gland which may grow or become infalmmated. The best treatment is surgical removal under local anasthesia and this is permanent solution. If it becomes infalmmated then it will be red with pus formation and urgent surgery would be necessary. So you should visit surgeon before infalmmation occur and then it can be easily removed.
Wish you good health. Regards