Hello,
You may have some trauma to the area causing a delay in healing. Are there any sharp teeth or irritating habits? Avoid all irritants including smoking and alcohol. Acidic and spicy foods may best be avoided as well. Rinse your mouth. Warm salt water is an excellent choice. Avoid alcohol containing rinses. Make sure you are not dehydrated and have no vitamin deficiencies. Take vitamin B12. Maintain good day dental care.
A benzocaine gel such as Zillactin may offer protection and relief. You may need time and have reoccurring episodes when stressed. Consider evaluation at an oral surgeon if the condition worsens.
Thank you for your inquiry. I hope that these suggestions are helpful.

Thanks for your query, I have gone through your query.
The canker like sore on the upper labial mucosa could be a traumatic ulcer or pahthous ulcer or pemphigus.
Consult a oral physician and get yoursefl examined to rule out these conditions.
If it is traumatic ulcer or herpetic ulcer, you can take topical anesthetic and analgesics like anabel gel. apply 3-4 times daily before food.
If it is aphthous ulcer or pemphigus, then you can take topical anesthetic and analgesics like anabel gel. apply 3-4 times daily before food and topical steroid like triamcinolone acetonide 0.1% 4-5times daily after food.
Do saline gargling. If the lesion does not heal in 5-7 days then consult a oral physician and get it examined.
I hope my answer will help you, take care.