All Nexus 5 come with a sim ejection tool, you can use the tool if you are at home. What if, you want to change the sim card on the go. You can't carry the Nexus 5 sim ejection tool everywhere you go, but you can find some useful things on your office table itself. You can use a safety pin or paper clip or anything that goes into that hole.
In order to eject the sim tray on Nexus 5, push firmly and gently until the sim tray pops out.