How do I fix my iPod nano after I washing machined it?

that sounds bad - the only way is to disassemble it completely

here is a guide to get the nano apart - but be careful - very tiny parts inside the nano ;-)

the best way would be removing the battery and clean everything with rubbing alcohol, check the connectors if anything is burnt or something like that, if possible - measure the battery - but i think it would have 0v and will not charge.

try to find someone with modern rc cars - the use the same battery type and the have special chargers- charge the nano battery for 5 minutes as a LiFe or NiMh and then as a regular LiPo - when the battery is full, resolder it (oops - i forgot to mention it, the battery is soldered on the logicboard) and maybe the iPod works again