first thing you should do is to try to dry out your iPod thoroughly don't plug it in or try to charge it in the meantime, in case you fry some of the electronics if still wet

in the best case you may be lucky and it might work again, some people have had such luck with personal electronics going through the wash, after drying it out for at least several days. (including myself, with a cellphone that at first seemed completely dead)

try dismantling your iPod and storing the parts covered in a bowl of uncooked rice to absorb the moisture. also take a look a the many other questions here on ifixit with the tags liquid spill or water damage - this is a VERY common thing to accidentally do to your iPod

you can get an idea of how to open your 5th gen nano in the teardown photos here.

without seeing if it shows some signs of life at all after drying it out, it's hard to tell what might have been damaged by the water. anyhow, I suggest being patient and try drying it out if you haven't already - then decide the next step