Levin,
I'm no doctor, so this is not a medical advice ....
The hand condition your mother had, might have been Dupuytren's disease.
A lump in your foot 'may be' Ledderhose, which as you know is related to Dupuytren's. You probably also know DP is considered family related.
So, like Anon wrote, go and see a doctor. If his 'proper advice' is to do surgery on your foot, run like hell and see another doctor first.
A layman's opinion !