hello, your sores- seems to be ruptured vesicular lesion.. most common are viral herpes infection.. these kinds of ulcers are common on lips and corner of mouth.. it is also associated with fever prior to vesicle eruption.. if your fever persists you can use paracetamol tablets to manage it.. your dietary intake of multi-vits and minerals is also reduced due to problem in swallowing.. so you can use anaesthetic gel/mouthwash to get relieve from pain during swallowing.. have ample of fruit and green leafy vegetable diet.. or nutritional supplements.. .. use antiseptic mouthwashes after meals.. avoid spicy food completely. these lesions resolve within 7 days mostly by proper diet in healthy individual.. and if they persists more than that consult oral medicine specialist as he may give you antiviral creams/tablets as required.. to confirm the diagnosis they may take biopsy for pathological examination.. other causes of such sores are autoimmune disorders- pemphigus,lichen planus, etc.. they are rare.. and a biopsy or immunofloroscence test is done to diagnose them..