Welcome to Healthcare-Magic
Thanks for the query.
It doesnt sound like cancer and this is probably some benign subcutaneous lesion such as lipoma
. If this was cancer it would grow more rapidly and you would have some other symptoms and signs. It can be surgically removed under local anasthesia and then sent to analysis to be sure but if you dont have pain or redness
around it I dont think that treatment is necessary at all.
Wish you good health.