Can you please tell me about lichen planus?

Ok. It is an autoimmune disease that causes the body's immune system to attack cells in the mucus membranes of the mouth and other parts of the GI system. It is usually treated with steroids and diagnosed with examination, history, and a biopsy.
See a dermatologist. Lp is often seen in the mouth, usually without any symptoms. Most often it presents as a distinctive skin rash which is very itchy. There is often a reaction to a med or infection as cause. Best treatment by experienced dermatologist.
Lichen planus. It is an autoimmune disease that has no real cure. It can come and go. Can appear like a lacework pattern on the oral mucosa, can also involve the mucosal linings of other parts of the body and can also show skin manifestations.