my ipod mini was disabled because i forgot my apple I.D. and password. How can I fixed it and open my ipod?

First

If you forgot your Apple ID - Apple Support

then

If you forgot your Apple ID password - Apple Support

However, I am a bit confused since yo do not use your Apple ID and Password to unlock the screen. However, yu do need to enter the ID and passwrod to activate an iPod

Find My iPhone Activation Lock

Forgotten Screen-Lock Passcode

Connect the iOS device to your computer and try to make a backup

iOS: How to back up

Then restore via iTunes. The iOS device will be erased. Place the iOS device in Recovery Mode if necessary to allow the restore.

If recovery mode does not work try DFU mode.

How to put iPod touch / iPhone into DFU mode « Karthik's scribblings

For how to restore:

iTunes: Restoring iOS software

To restore from backup see:

Restore your device from an iCloud or iTunes backup - Apple SupportIf you restore from iCloud backup the apps will be automatically downloaded. If you restore from iTunes backup the apps and music have to be in the iTunes library since synced media like apps and music are not included in the backup of the iOS device that iTunes makes.

You can redownload most iTunes purchases by:

Downloading past purchases from the App Store, iBookstore, and iTunes Store

If problem what happens or does not happen and when in the instructions? When you successfully get the iPod in recovery mode and connect to computer iTunes should say it found an iPod in recovery mode.