If you did the type of reset that will try and save your personal data, and there was an issue on the device, this can happen. The way to get access would be to do a "Hard Reset" which will fully wipe the device of anything added to it and reinstall the OS.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the "Volume Up" buttons...