When you cut down to NanoSIM size there's a risk of damaging the SIM contacts because not only does the plastic need to be taken out, but you also need to cut into the copper surface itself. ... Even if you use one of those “certified” cutters, you can still damage the SIM contacts.

What will damage a SIM card?

Whack your card several times with a hammer, until the SIM breaks into several fragments. Toss these pieces out in separate trash cans, so no one can find them. There's no right or wrong to cut up or smash your SIM card. What matters most is that your card is destroyed, and no one can get their hands on the data.

Is it OK to cut Micro SIM to Nano?

As you can see, Nano-SIM cards are slightly thinner than Mini- and Micro SIMs. Nevertheless, even if you cut a Micro-SIM to fit into a Nano-SIM tray, you should be just fine.