If the computer continues to stay on that screen and not boot do the following:
Power down the Mac.
Hold down Command-R on your keyboard immediately after pressing the power button to turn on your Mac.
Continue holding until you see the Apple logo or a spinning globe then release the keys.
In the Disk Utility application, select the disk or partition to check — which in this case is the system partition is named “Macintosh HD” by default — and then click the “First Aid” button.
Note that the First Aid function can run on an entire disk, or an individual partition depending on what you select.
Select Verify Disk Permissions, then select Repair Disk Permissions if that button is not grayed out.
Then select Verify Disk, and once it completes select Repair Disk if that button is not grayed out.
After running the utility, select Startup Disk in the Apple menu.
Select the startup disk for your computer.
Restart the computer and test to see if the issues are resolved.