I have been diagnosed with severe erosive oral lichens planus by biopsy. Had it for 4 years now. It was so bad a few years ago that I lost 30 lbs because eating was very painful and difficult. I could not even touch my face on the outside with causing pain. Going on the assumption this is an autoimmune disorder, I have tried many things. I am managing now, so will share some things with the group. This is not an advertisement. I am listing products I've used that helped me in my own personal experience and will share some of my tips. Since digestion starts in the mouth, eating healthy to improve gut and function could help (especially for leaky gut condition which I have).

I stopped all NSAID use; I was taking Mobic(r) or meloxicam which is a very high powered NSAID that probably caused leaky gut condition. I think the NSAID is what started it all. Also was applying NSAID topically as gel form "Pennsaid".
Got tested for food allergies - see below
Get teeth cleaning every 3 months
Swish & spit with coconut oil before eating and all the time
Brushed teeth with coconut oil
Use water flosser on lowest setting
Stopped using big name brand toothpastes. Tried these: Squiggle-thumbs up, Peelu-doesn't burn but is a bit gritty, no flavor, charcoal DIY - AVOID ANYTHING CINNAMON AND MINT
Used COCONUT oil for oil pulling, and swished some in mouth before eating which can make eating tolerable
Glutamed by NuMecica- medical food (not RX) - for cell regeneration support, I add some licorice drops (non-alcoholic) since licorice is supposed to act like steroids. Still use this for flare-ups:
"Healthy Teeth and Gum Mouthwash, Super Effective" product from Dr. Arenander's product line. This does have peppermint oil but not enough to bother me.
Gelclair Rx of hyaluronic acid
Lidocaine topical, viscous - RX
Vitamin D - I was deficient so replaced by RX for 2 months and level is normal now
Positive for gluten intolerance by saliva test.
Food allergies - sent in samples of hair and a buccal swab. I'm not quite sure if allergies were tested on hair samples (which would be less accurate I think) or the DNA swab but were listed for MANY:
->chicken meat, beef, veal, black tea, cheddar cheese, cinnamon, components of egg and dairy, tomatoes, strawberries, gluten, cacao (chocolate), walnuts... THEREFORE, I have tried to cut out many of these items just in case. I did a 3 day cleanse consisting of smoothies & gluten free / vegan soups, everything dairy & gluten free and I had significant improvement. I now have 1 or 2 of these usually daily. Interestingly, a drink with lemon juice, cayenne pepper, and pomegranate seemed to do good. I tried this of course after the improvement because I would have never considered ingesting lemon or cayenne pepper while flaring-up.

Stress causes flare-ups. I use melatonin for calming.
The oral surgeon prescribed Lidex gel, which is not meant for application on mucous membranes, so it stings. I only use with absolute severe flare-up.
I have taken Medrol Dosepak (steroids) before. First time it seems to help but not after that. I was put on low-dose prednisone (steroid) for a year but that didn't help.
Have not tried any RX immuno-modulators like Imuran; have not tried Dapsone.
I think my nose is mildly affected. I think my eyes are affected too as I am getting stents put in tear ducts since they are blocked from tear drainage by inflammation.
Suffering is horrendous!
Will end here for now.