Hello,
Thank you for asking your query.
From your descriptions it could be a possible herpes simplex (Cold sore) with a secondary bacterial infection. The second possibility is a atypical canker sore - Aphthous ulcer.
Cold sore need not be always recurrent. It can occur just once or for a couple of times. And the presentation can largely vary. They need not be that frequent and painful and recurrent. Since you have a history of canker sore, this could just be canker sore too. If the particular lesion has undergone some trauma or friction it can look atypical.
Anyway other primary 'infection' is not likely. If you are immunocompetent ( adequate immunity - no diabetes, cancer medication etc) a bacterial infection or abscess is not likely.
So its reasonable to conclude this is a cold sore. However to confirm you will need further testing. For now I recommend you the following :
• Avoid eating acidic foods such as citrus fruits,
tomatoes, pickles, or other foods such as salty
snacks if they irritate your cold sore.
• Rinse your mouth as often as necessary with a
commercial mouthwash product or a solution
made by mixing one teaspoonful of salt in 500 mL
of water. These remedies will help soothe cold
sores and reduce irritation.
• Cold sores are contagious. Avoid contact with
other persons during the period when the blisters
are developing. Try not to touch your eyes or genital area unless you have first washed your hands
thoroughly. Avoid oral sex during an episode as
this can transmit the infection to the genitals.
• Gently wash the lesion area with a mild soap-free
liquid cleanser and pat dry with paper towels.
• Discard used towels. Wash your hands carefully
with a liquid cleanser and water and keep them
away from cold sore lesions as much as possible.
• You may take analgesics such as ASA, acetaminophen, or ibuprofen to help relieve the severe pain
of cold sores. Be sure to follow the directions for
use. Children should not take ASA.
• Keep cold sore lesions moist to prevent drying and
fissuring.
• Use a sunscreen of SPF 15 or greater on your lips
and over the area of your face where cold sore
blisters develop.
• Don’t touch reusable applicators (lipsticks, lip
balms, etc) directly to the cold sore; apply with
a finger or other applicator and wash or discard
immediately, as appropriate.
Antibiotic oinments can help if there is seconday bacterial infection. Please contact your Doctor regarding this. Other than this you need not take any specific medication for this.
Hope this helps.