When you post, stop and take a breath, use punctuation, sentence structure and paragraphs so we know what your issue is.

As best as I can dope it out, you're wondering if it's possible that you somehow got the valve stem nut trapped in your rim.

If that's your question, the answer is probably, but not likely. Most double wall rims have no liner at the valve holw so it's possible for something to drop between the walls. OTOH, once the valve is in place that entry is closed so the only way the nut could get into the rim is if you somehow broke it off while inserting the valve.

Odds are that the rattling you hear in the rim is some left over debris from production. Often the drilling and eyeletting (if any) leaves small chips still attached to the insides of the holes, and these break off over time causing rim rattle. It doesn't matter, since once the rim spins they stop moving and don't make any noise. If you're really patient, you can sometimes shake debris down to the valve hole and out when there's no tire mounted, but I never bother since they never rattle at over 2-3mph.

As for the valve nut, you probably broke that off when pumping the tire. It doesn't matter that much since the valve doesn't need it to stay closed, but without it you cannot use a pressure gauge. If you take a few minutes, there are plenty of threads discussing broken PV stem nuts, and how to prevent them so I won't bother repeating this oft posted info.