You killed the ender dragon and now you don't know what to do with the egg?
How about using it to manipulate time?
Place the Time Manipulator on the overworld.
Upon right clicking it with a Infused Gem it will shift time!
Right clicking with a Day Infused Gem will cause the time to go backards until it's day time.
Right clicking with a Night Infused Gem will cause the time to go forward until it's night time.
Tired of time manipulating? Get your dragon egg back: