Hello @Jeannie1!
This is going to depend most on how you feel about- but I personally say yes, it will be fine! 
The day of the Full Moon is when the moon is 100% illuminated. The next day it is labeled as a Waning Gibbous- but it is still 98-99% illuminated (depending on the exact time of the full moon the day before). The light has only decreased by a tiny fraction! You can check the exact percent of the moon’s current illumination on the Moongiant Calendar 
Looking up at the sky with your naked eye the day after a full moon will look exactly the same as the full moon. To me, I consider that extremely close to being full and still possible to draw energy from.
But keep in mind that if you personally feel that once the full moon begins waning, the energy can longer be accessed- that will carry over into your spellwork. Remember, your intent is the most powerful ingredient in any magic you do! 
In this case- you can still make your moon oil! Instead of using the properties of the full moon, consider drawing on the different energies of the Waning Moon- the benefits of the moon as it moves towards a New Moon 
Good luck with your moon oil and blessed be! 