Only thing I can think of is a factory reset.
I believe the combination is Power+Volume Up+Volume Down (when your phone is off). If that doesn't work, press power then when you see the Acer screen press Volume Up+Volume Down.
If that doesn't work, access recovery and do it there ( 1) Remove/Replace Battery, 2) Hold down Power+Camera+Volume Down until you hear 2-4 vibrations, 3) Press Power+Camera). Once in recovery, I think you press the camera button (I have never used stock recovery. All I know is that you will see a little Android robot with a caution type sign. If camera doesn't work, try other buttons until you see options, you should find a factory reset option or something along those lines).
You would lose the contents of your phone.