Thanks for your query.
Well, without a clinical evaluation it would be difficult to determine the cause of the lump. Possibilities that may need to be considered include , lipomas
, exostosis(benign bony outgrowth), growths from underlying connective tissue
I would suggest getting this evaluated by an orthopedician for an accurate diagnosis and appropriate management. He may get the X-ray of the area affected and FNAC (fine needle aspiration cytology) of lump under his/her guidance
I do hope that you have found something helpful and I will be glad to answer any further query.