I tried installing debian on a USB stick. I believed I made a mistake with the grub boot up part. I want to leave my harddrives alone and with my bios choose to boot up from a stick. Do I need grub if linux is the only OS on my stick?

I believe I selected the USB drive I was using but I think the next step asked about /dev/sdX which I left as blank (didn't I just say install for that drive...). I'm not sure how to know which sdX it is because I'm install from a USB stick as well with the same name.