Hi yes this is an ulcer , biting onto which has increased the size.
Yes you can apply dologel or even Anabelle gel on and around the ulcer with a q-tip and leave it for about 10 to 15 mins thrice daily.
Avoid hot and spicy food which may increase the pain and burning sensation.
In addition Vit
B12 supplements can be taken once daily for a month.
Also keep yourself hydrated.