that can happen if you have usb as 1st item in boot order. You shouldn't have anything in boot order yet, and instead use Boot override that is on the boot tab - just scroll down.
Put usb in PC
go into bios and go to boot tab
scroll down and choose boot override
choose USB from list, PC will restart and use the USB One time, and then it should use the HDD or ssd
I would show you the item in your manual but Asus, like many MB makers, doesn't show all the BIOS commands in the B550 boards, but does in the X570 boards
See page 3-18 -
https://dlcdnets.asus.com/pub/ASUS/mb/SocketAM4/ROG_STRIX_X570-F_GAMING/E15827_ROG_STRIX_X570-F_GAMING_UM_v2_WEB.pdf
Its 8am here, I been awake all night so my ability to help is limited.