I have a really bad canker sore in the back of my mouth. it hurts to eat,open my mouth and talk what can i do to relieve the pain?

Magic mouthwash: Is Benadryl, (diphenhydramine) Maalox, and Lidocaine mixed together with a prescription at your pharmacy. Your doctor can call it in. You might want to gargle with it.

Pain: from a canker sore generally lessens in a few days, and the sores usually heal without treatment in about a week or two. If sores are large, painful, or persistent, your dentist may prescribe an antimicrobial mouth rinse, a corticosteroid ointment, or a prescription or over-the-counter solution to reduce the pain and irritation. REF: WEBmd

See Dentist: Self diagnosis may be inaccurate at best, dangerous at worst. Please see your Dentist for N evaluation and appropriate treatment.

See a dentist: some ibuprofen right now is likely a good idea, but definitely see a dentist ASAP

Canker sores: is the most common oral lesions. Most ulcers, infections will clear up by themselves within a week or two. You should see your GP or dentist if the ulcer gets worse or lasts for longer than 2 weeks. Best of luck.

Canker sore: canker sores are commo oral ulcerations that will heal in 7-10 days. They increase when under stress or from trauma and other reasons. Avoid hot, spicy foods. OTC medications can help. If it does not heal, gets worse or you get them frequently see a dentist

Lasers can help: A dentist with a laser can help you. Using what is known as photobiomodulation (or biostimulation) the healing time for mouth ulcers can be reduced to a few days and pain relief is immediate. For more information follow the link...http://www.laserdentistbaltimore.com/mouth-ulcer-and-cold-sore-laser-treatment/

RX medication: Have your dentist run a culture of the canker sore and a useful Rx would be Kenalog in Orabase oral paste. Rinse mouth with a combination of liquid Benadryl (diphenhydramine) and PeptoBismol.