Don't cut it yourself. Micro and nano sim is on a different league. It's easy to cut a micro sim but nano is more difficult. It would cost you about 50-150 rupees to get it cut, depending on how good you are at bargaining
Btw, just walk into any mobilink office and get a brand new nano sim with your phone number. Takes about 15 minutes. Just make sure you're the owner of the SIM card and you've got your CNIC card with ya. Or the owner is with you.