Hi @Buddl, welcome to our forum!
If you have a Google account in your device and you have activated the MyXperia service, you can try and log in to this service at the link below.
myxperia.sonymobile.com
Find and click on your Z2 Tablet > wait for the service to locate it (needs an activate network connection) > click on "Lock" and enter a new PIN code for the device and unlock the screen lock with that code.
If you haven't activated the service in your tablet, you will need to perform a software repair using Xperia Companion to get rid of the screen lock. Do note that this will delete all data stored on the internal storage of your tablet and since you can't unlock the device, you can't create a backup.
I hope that helps!
