Thanks for posting your query.
Without a clinical evaluation it would be difficult to determine the cause of the lump. Possibilities that may need to be considered include lipomas
, cysts, growths from underlying connective tissue
This lump might compresses the nerve in its vinicity and is the cause of numbness
I would suggest getting this evaluated by an orthopedician for an accurate diagnosis and appropriate management.
Wishing you good health
Dr Saurabh Gupta