If a nest has been disturbed, cover it back over as best you can and leave well alone. Mum may or may not be in the nest with her babies but will hopefully be close by if not.
She should return several times throughout the day to feed her babies. Upon her return, as the nest has been disturbed, it is possible she may abandon it or relocate her babies if she thinks they are under threat. It is also possible she may kill her babies. You can place some loose material such as twigs or grass around the nest. Check regularly to see if it has been moved indicating that mum has returned. Observe from a distance and if you have concerns contact your local wildlife or hedgehog rescue for advice.
If a nest has been destroyed, contain mum first as she will run off. Use a hgh sided box or container that she can't climb out of. Place some flat newspaper on the base and hand tear some more to cover her over. Wear gloves and gather as much of the nest material as possible and place it and the babies in a seperate box to mum.
Phone your local wildlife or hedgehog rescue for advice.
In both cases it is important to place the boxes in a dry place and out of direct sunlight. Cover the boxes with a towel or piece of net curtain to keep the flies away.