I forget my applock password

[AC Question]

I apply the password to settings, playstore, install/uninstall, chrome, file manager, and others. I didn't use my phone for a long time and I forget my password. There's no "forget password" option in the applock. I have no idea to get out of this problem. I can't even open my settings or install another app to do the installation of a new file manager. Please help me ;(