DClark: Grapeshot bombs. If you have some equipped it'll allow you to blow up the nest with a mouse click when you stand by it.

FluxMorz: You buy the recipe off Cedric I think, and once you have it, meditate, open your alchemy window and make I dunno 5. Then equip them to your pockets in your inventory and head back out. When you see a hole in the ground amongst a lot of blood and bones, walk up to it and you'll be able to click on the hole (like picking up an item) and Geralt will place the bomb, then just run off a bit and it will explode, destroying the nest.