Passcode requirement message in endless loop

I have an Iphone6 and after I put in my passcode yesterday, a pop up message came up. It says "passcode requirement, to change your passcode, first enter your current passcode" I did not ask for this, it is just keeps popping up. After I put in my passcode again (which clearly is the correct one because it initially letsme in) I hit the continue button and I get the same pop up again. It is an endless loop that I cannot get by and cannot use my phone period.. any help would be appreciated greatly.thanks