Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern..
As per your complain a sore behind the last molar that is slightly tender on touch can be a
canker sore or can be due to
injury to the area with any hard food.
It can also be bacterial infection in that area if there is any left out root piece or foreign body impacted in that area..
I would suggest you to consult an Oral Physician and get evaluated and a thorough clinical evaluation and an
x ray of the region if required can help in diagnosis and treatment can be planned accordingly..
As of now you should do warm saline gargles 3 to 4 times a day..
Apply antiseptic ointment over the area..
In case of pain lignocaine containing gel can be applied..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora..