I Have Developed Lumps/knots In The Palm Of My Right

I have developed lumps/knots in the palm of my right hand. first it was just one, then a larger one, now another. I also have a few in the bottom of my feet. Asked my doctor at my check up he said it was no big deal a heredity thing that if they keep coming and start causing problems can be fixed. What are theses? appear to be on tendons.