What Could Cause Multiple Small Painless Bumps Under The Skin Of My Arms That Now Cause Pain With Movement?

I have dozens of small (maybe 1 cm wide) bumps under the skin of my arms. You cannot see these bumps - they cause no rash or irritations of the skin but you can feel them but now that there are so many - I am finding pain in my arms when I move them in certain ways - I am GUESSING ( I am not a doctor), that the bumps are affecting the nerves. What are these bumps? My first doctor when I got the first bump said it was calcium deposit but recent doctor said no but said he didn t know without a biopsy(sp?). Any clues?