Move grub from USB to HDD

I install Ubuntu from USB. After complete installation I reboot my PC, remove flash frive and try to boot to linux. But I can’t. because grub installed into flash drive and I see text:

grub rescue>

When I insert USB flash I see normal grub menu and boot into linux or windows.
How to reinstall grub into HDD and boot without USB flash?

What if when booted to Ubuntu you do this:

grub-install /dev/sda (or whatever disk your primary disk is)

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