Common question I know. What do you do if you've forgotten your admin account password? I have access to my user account but when I want to change something in the system preference settings (i.e. change a screen lock duration) and it asks for my password I am dumbfounded. This is the password asked for when you click on the padlock icon. I used the same password for years but have not happened to need in there for about half a year so I am utterly blank. Old age.
iMac 2012 OSX 10.12.6
iMac 2012 OSX 10.12.6