You can do this by adding the following qualifier to your search query:

created:@today

Unfortunately this feature is not mentioned in the relevant documentation, so this related documentation for GitHub Projects is the closest thing to an authoritative reference:

https://docs.github.com/issues/planning-and-tracking-with-projects/customizing-views-in-your-project/filtering-projects#filtering-for-when-an-item-was-last-updated