Hi there are many causes of lips burning ranging from mild to serious. Mostly it is not serious and do not pose a significant health risk. It might occur as the result minor trauma like biting your lip or burning it with hot food,contagious(herpes simplex virus),canker sores(known as aphthous ulcers). Treatment is mainly depend upon the underlying cause but symptomatic treatment is helpful as in most of the cases the cause remains unknown. You can see your family doctor or surgeon to rule out any other infective or malignant pathology although the chances are rare. Here, I am giving you some information which can be beneficial to you. 1) Maintain good oral hygiene and avoid hot and spicy foods. 2) Antiseptic mouth wash(chlorhexidine) for gargles for rapid healing and to prevent secondary infection. 3) Topical analgesic gel like benzydamine which is also having a local anaesthetic effect. 4) Take folic acid with vitamin b complex to promote healing. Hope this information is helpful but it would be advisable that you will see your doctor first and then ask for treatment. Thanks.