SIM PINs are different from the PIN you use to unlock your phone’s screen, and most phones do not have SIM PINs by default. If you see a message on your phone that says “Locked SIM” or similar, you’ll need to enter the SIM PIN to do anything on the phone.
Fortunately, your mobile provider will provide you the PUK so you can reset your SIM. You’ll just have to prove your identity over the phone or at an in-person location. If you’re not sure who your provider is, remove the SIM card—you’ll see the provider’s name there. Some providers let you see your PUK when you log in to your online account. Look for an area of your account dashboard called something like “SIM” or “SIM Card,” which should have a sub-area called “PUK” or similar. [3] X Research source
