Decided i would change my strings to a lighter gauge, while taking off the low E and the a string my nut just fell off, can i just superglue it back on or what?

yeah if your nut is still in one piece then just superglue it back on, clmp it and leave it for like a day thats what i did and my guitar is fine. just make sure you dont out too much on so it like spills out the sides or raises the nut too much.
If it's a cheapo guitar, go for it. If it's a more expensive one, don't use super glue. Nuts are usually glued in with a different type of glue. Using the wrong type can make it more difficult to remove in the future.
With all the strings on, the pressure should hold the nut on. I wouldn't bother gluing it unless it refused to stay put.
'08 Fender American Deluxe Stratocaster
Boss CS-3
Vox Satchurater
Peavey Classic 30

Fender Jazz
Carvin BX500
with a sharp tool, carefully remove the old glue and clean. then clean any glue from the bottom of the nut. apply adhesive of choice and clamp for at least a half hour. then restring and you're good
Right. Normally, string pressure holds the nut in place quite nicely. DO NOT use superglue...There is every chance that wood will pull away at such time you need to repair or replace the nut.
Just a drop of any decent wood glue should be fine...I use Titebond.
omg, no - don't superglue it!!!!!

Bikewer is correct. most nuts are held on only with string pressure. a SINGLE drop of titebond will hold it on if you like, but only one drop.
Just to reiterate, clean the old glue as cocksmith mentioned and use wood glue(a drop is plenty as Bikewer and patticake had mentioned). I hate repeating what has already been said, but just wanted you to be able to tally the comments and know the right way to do it.
Even a tiny drop of Elmer's glue will do the trick. You should be able to take off the nut with very little effort in the event that it needs to be replaced.
Quote by Ur all $h1t
On public transport I furiously masturbate while trying to make eye contact with as many people as possible for as long as possible.
and actually you don't need any glue at all. the strings will hold the nut on just fine.
What about some type of shim? Like a split piece of toothpick or something to wedge in to tighten it naturally.