Your budgie is a sky blue greywing yellow face type II clearflight pied.
He is very young, looking at him I'd say he is 3 months old, he's clearly not gone through his first moult yet.
His cere will change colour at about 6 months old but this doesn't mean he will be ready to breed. Budgies are only fit to breed after they reach adulthood and this is after reaching 1 year of age.
It's never a good idea to place a nest box or any other type of nesting areas on a cage as that would only encourage breeding behaviour which will lead to unwanted egg laying.
In order to avoid complications and since you don't yet seem to have a good grasp of the species nor the required experience in budgie ownership, it's not at all advisable to allow your hen to lay a full clutch of eggs or to let her breed.
Please remove the nest box, discard the egg and follow the recommendations on this link in order to break your hen's egg laying cycle: