Rarely oral cancer. Chronic oral lichen planus can in a small percentage develop oral cancer. Topical prescription creams such as retin a (tretinoin) can be used in the mouth to treat oral lichen palnus. I have experience with oral Metronidazole as a treatment for lichen planus with good results. You need to be checked for hepatitis C which can be associated with lichen planus as well as review drugs as contributory cause.
Possibly. May increase your risk for developing squamous cell carcinoma from being chronically inflamed. May also be seen more commonly in patients with hepatitis C so get checked. I would see a doctor, get a little steroid cream such as Lidex (fluocinonide) gel to reduce the inflammation, get your blood tested, and get regular oral exams looking for non-healing ulcers or nodules. It is not contagious so kiss away.