What kind of product would seal the spaces between floor planks that have shrunk.?

I live in an older home and the entire 2nd floor is one large room, 15' x 25'. This is my sewing room and the spaces between the 5" wide pine floor planks are collecting needles, pins, pieces of thread, etc. The vacuum won't remove them once they are embedded between the pieces of wood flooring. I would like to fill the spaces with some kind of wood putty, or something thick enough to seal the spaces to prevent parts of my sewing projects being embedded in the floor. What kind of product could I buy or make that wouldn't cost me an arm and a leg?