Maybe someone else has a better idea, but I'd probably do a factory reset. This will wipe the device clean, so you will have re install and configure some apps. Before you do a reset, make sure you're connected to your Google account and have sync'd. Once you've done the reset and entered your Google account info, contacts and installed app (including paid) will return. Unless you specifically back up the data, you may lose your progress from any installed games. How and if you can back up game progress depends on the game.