Hi,
Thanks for your question.
As the lump is painless, skin color it is most likely a lipoma.
Lipoma is a abnormal over growth of fatty tissues, it ha no particular reason.
Usually
lipomas are harmless.
There is no medical treatment for it.
It required surgical removal in following cases-
1) Cosmetic reason -Some may look odd.
2) Painful - rarely become painful.
3) In some cases lipomas near joint may restrict joint movement.
You can wait and watch it.
But you should consult surgeon in case-
1) Rapidly increasing size.
2) Change in overlying skin color.
3) Become fixed ie. can not moved.
4) Development of pus point.
Hope I have answered your question. Please do vote.