What can be done for untreated 'lichen planus' - the lining of my mouth is swollen and sore, and front of tongue is numb, same as roof of mouth- ali?

Lichen planus. Special gargles containing anesthetics and anti-inflammatory medication often help reduce symptoms. If this topical treatment is not helpful then a brief course of steroid pills will likely help. If this persists, make sure it gets a biopsy to rule out other causes.
Corticosteroids. While this will often go away on its own, it may take months. See a dentist as there are prescription medications that can help reduce your symptoms but you will need to be professionally evaluated first.