I've cut a ton of SIMs with kitchen scissors, just be careful and always trim less, not more, than you think you need. The worst thing that happened was I cut one a little too small and it slid around inside the tray so I taped it in, but the contacts still worked fine.
If your carrier is named Rogers, for example, google search Rogers nano SIM and look at how the SIM contacts compare to yours. Trim accordingly.