They usually keep the nest clean. I would try to avoid handling eggs as much as possible as oils from your skin will clog some of the pores. Same thing with water if you let an egg remain wet any length of time. You will suffocate the egg. It's best to just let the parents take care of it.
Budgies are usually very good parents, and USUALLY if they reject a chick it's for a reason - the chick is already sick or weak. And it is very difficult to handfeed a very young budgie even if healthy. If you notice a chick that is not being fed by the parents and you know how to handfeed you can offer a supplemental feeding or two to help it get its strength up to beg with its siblings.


Karen
Chico (conure) and Pippin (budgie)
WI