OK something is going on that isn't making sense here. Try starting up the tablet then in "Safe Mode" and see if it will allow you into the "Settings". If not, then you need to either "Hard Reset" it (which will wipe everything) or have it looked at.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.