Only solution,Hard reset your phone and do a reset factory settings in recovery mode. BTW which phone model you are using, I guess it must be Samsung :)

updated
-
One more way, if you know your phone is rooted and ADB on..
You have to delete all your key files from system folder. Try this.
Connect you device with usb and run following command. If you are not able to do so, i am afraid. You need a full wipe.

    adb devices
    adb shell
    cd data/system
    su
    rm *.key

Even if shows lock screen after reboot, try a easy random pattern/password.