RedHat 7 attempts to boot from USB

I have a recently ordered Dell Precision T7810 that came pre-loaded with RedHat 7. There were some initial issues that caused the need for a re-installation of RedHat, which was done from a bootable USB. Since then, when the computer is rebooted, it attempts to boot from the USB even though it has been removed. I was wondering if anyone had any advice on how to prevent this from happening?

I am very new to managing a RedHat system, so if there is something obvious I've neglected, please tell me.