Don't worry - the following procedure will not delete your games' save data. Clear your console's cache by doing the following steps:
1. Turn off the PlayStation 4 by pressing the power button on the front panel. The power indicator will blink for a few moments before turning it off.
2. Once the PlayStation 4 is off, press and hold the power button. Release it after you have heard two beeps: one when you initially press it, and another one 7 seconds later.
3. Connect the DualShock 4 controller with the provided USB cable and press the PS button on the controller.
4. Choose "Rebuild Database".