Resetting jailbroken device in settings caused boot loop
Resetting a jailbroken iOS device using the option in settings will cause no end of bad things, usually resulting in a device stuck in a boot loop, which appears to have been the case here.

You'll have to restore your device in iTunes. Connect your device to iTunes, then hold power and home until the screen turns off and back on with the Apple logo, then let go of power but keep holding home. Once the device appears in iTunes, restore it.