I need to reset keychain becuse i put my house phone

When i was about to erase the computer to restart it asked me for the phone number. Not knowing which one to put i put the house phone. When resetting it asked me for the verification nuber that was sent to the phone number. I could not get to the phone and the code was lost so how do i reset keychain on a mac mini from late 2012 and running on mac OS X Yosemite Version 10.10.3