If you have optic nerve atrophy can it worsen over time?

Yes. If the cause of the optic nerve atrophy is never treated it would progress.
Optic atrophy. The ophthalmic literature shows that vision loss can progress in some individuals with optic atrophy depending on the cause of the atrophy. For example if the atrophy is from optic neuritis and the person develops another episode of optic neuritis, further vision loss can occur.