edit/delete "custom label" for phone numbers

I selected "add new phone" when editing a contact, then in the drop-down menu with the mobile/home/work options, I chose "add custom label" (at the very bottom) and created a new label. How can I delete that label, since I don't use it anymore? Now whenever I add a new phone number to any contact, that label shows up as a potential option. It's not a huge deal, but a minor annoyance and I'd like to delete it but don't know how.