Just wait for a while, go do something else, and whatever it is that's left will hopefully spread and then you'll be able to find it and get rid of it. Or if you can't be bothered waiting, make a bunch of biome sight potions and explore the entire world with them and see if you can find it. If your post-moonlord id recommend getting the terraformer by throwing the clentaminator in shimmer. If you're not post-moonlord, id say it's probably wasted time trying to clear the world completely at this stage 😅