Well....when the pinion nut comes off....or just loosens up a little....I know the terrible noise that happens cause it happened a couple times to me back in 87....the end of the pinion teeth are basically grinding into the limited slip casing....even though the noise sounds like death it's probably doing nothing except cosmetic damage. Odds are in your favor no damage.
You can try a combination of blue loctite and staking...I personally would not hesitate re-using a damaged nut with Loctite. I suppose you wouldn't hurt it anymore if you tried snugging the nut and feel the companion flange rotational play....if it still feels loosey then tighten it more....then more ....then more...until it feels too tight(whatever too tight feels like) then back it off a little until it feels a bit loose and stake it. That's the quick fix. good luck. <img src="/forums/images/graemlins/kewl.gif" alt="" />