First off, congratulations!
To answer your question, the background check is basically looking for any criminal records that you may have, and not immigration status so you are safe if you have not committed any crime that would raise a red flag. This is an assurance to the hospital where you are doing your clinical rotations.
I do remember doing the background check through online, but you need a social security for that. I don't know if you have one, but it would make things easier for you if you did.
If you don't have a social security it might be a little trouble for you, but I bet you can get through it.
If you have any question feel free to message me.
Good Luck!
Just a suggestion, buy an NCLEX review book so you can practice and have a summary of your reading before an exam. It will help a lot!