Usually I disassemble completely if the interior of a pony is going to / has gotten wet. That means head off, tail out, and both left separated from the body for days/up to a week to ensure all the moisture has had time to evaporate from the nooks and crannies. Your milage may vary depending on the relative humidity of your room(s).
If the ring shows no sign of rust, then it's safe to put it back in as long as the pony isn't going to be in a very humid environment or dunked regularly in water in the future.