Finchluv
Hi,
Take out the 3 big ones and place safely at bottom of cage.
Remove tiny baby and check for life.
If dead, bury or dispose of body.
If alive, whip up a batch of warm hand feeding formula and carefully feed with tooth pick or handfeeding syringe.
Keep baby warm and safe, and continue feeding every couple of hours, until baby comes around and starts begging.
At that point replace baby in the nest, and watch to see if parents are feeding. If not handfeed until parents take over.
Goodluck