Help! I just had an accident...

I am by no means a car person but I stumbled across this forum and thought maybe one of you could help. I was involved earlier today in an accident in which i rear-ended somebody. It appears as though it was just body damage and I managed to get the car home fine. It seems to drive fine, but when i rev it in park i hear this "dropping" noise at around 4000 rpms.... now I have heard of a cars rpms being limited in park/neutral as to not hurt the engine. Is this the case or should I be worried? btw, i got up to 5 - 6 rpms in drive with no problem.

yes that is the rev limiter when you are in park and neutral and you are reving the engine.