As AJ397 states you have liquid damage and an ongoing short.
One thing that you can try is to dry it out completely using a powerful desiccant (drying agent). Some will say to use rice but you can jump right to the professional choice instead. First, turn the iPod completely off. Then, go to your local craft store (e.g. Hobby Lobby, Michaels, etc...), look in the flower drying section, and purchase a bag of Silica Gel beads. Once home, put the beads in a Zipplock bag or other small sealed container, wrap your iPod in a paper towel (so the silica doesn't get into the ports), place it in the bag, and seal it up. Place the bag in a warm part of the house and leave it for at several days. Then, remove it, plug it in to charge, and see if it goes back to working.
Silica gel beads are what labs use to desiccate samples and it will aggressively remove all water vapor from the air in the container, which greatly accelerates evaporation within your iPod. Once the liquid is no longer shorting out the circuitry in the iPod, it MAY go back to working if not permanently damaged.