Should I cover an underground nest in my garden to protect it?

Hi

I have found a nest in my garden between a supporting foundation wall and the soil next to it - it's just underneath the surface level but is exposed.

We have regular fox visits in the garden so I have covered the nest with a board and breeze block to protect it from the foxes - the mother bird can still fly in an out from the side but there's now not really much natural light to it.

Should I leave it exposed or covered?

Pictures attached to help!

Thanks

Matt