Upgraded to Big Sur. Now being asked for Administrator name and password which I don't have!

Upgraded to Big Sur on my 2013 MacBook Air. Now being asked for Administrator Name and Password to undertake certain tasks. This never happened previously versions of OS. Furthermore, I do not have these details. Going into System Preferences I am the only listed user and 'standard' not 'administrator'.

I am the only user of this computer and I set it up back in 2013.

Is there any way around this problem?