Since when you have this lump?
Is it increasing in size?
Can you move the lump?
Is it hard or soft?
Is it related to underlying bone?
Are you sure it was not there two weeks ago?
Is there any tenderness or redness?
does it look like toughened and thickened area of skin?
Or something below skin?
Thanks for all the information,
If there is no pain or swelling or redness infection is less likely cause of lump.
Possible cause of this lump can be benign soft tissue tumor like subcutaneous fibroma , lipoma or ganglion cyst.
Other possibilty is of a callus.It is a toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation.
Do not worry all these can be treated easily.
You might require surgical removal.
Since there are no symptoms, there is nothing to worry about.
You should contact you doctor and get your self exmained by you doctor to know the exact cause.
I hope this helped.