Hi Wilfredo,
You might just have a corrupted file in your firmware. The skull logo suggests the iPod was [https://en.wikipedia.org/wiki/IOS_jailbreaking|jailbroken|new_window=true] with the [https://en.wikipedia.org/wiki/Greenpois0n|Greenpois0n] jailbreaking software. If you didn't jailbreak the phone yourself, the easiest solution might be to put your iPod into [guide|52826|DFU|new_window=true] (Device Firmware Update) mode and [[iPod Touch 2nd Generation Troubleshooting#Section_Corrupted_software|restore it with iTunes|new_window=true]]. If you're already familiar with jailbreaking iOS devices, you can just try jailbreaking the iPod again.