Oral lichen planus in many people does not cause any symptoms. There is no need to worry.
One of the main causes of OLP is stress. So do relax, you could do some meditation or yoga and so on.
Biopsy provides best diagnosis. But if you have only pigmentation and mild changes, and are not willing for biopsy, pl be under a regular follow up with an oral medicine specialist.
Next Steps
Diet by itself will not have an effect on OLP. You can consume a good balanced diet with fresh fruits and greens.
If you have any adverse habits such as smoking or chewing tobacco, stop immediately.