This pin holder lets you store your pins by attaching them to the pinboard itself.
The container is fixated by 3 magnets on the other part, which is secured to the pinboard with two pins.
You may need to make the holes in the container a bit less egg shaped if you print without supports to make the magnets fit better. I used cheap magnets from Amazon with a diameter of 8mm and a thickness of ≈ 1.7 mm.

Printed with .4mm nozzle and .2mm layer height.