Canker sores are just
mouth ulcers on the inner lip, right? (We don't use the word "canker sore" at all here, nor distinguish between ulcers on the inner cheeks or lips).
Anyway, when I've had ulcers that have pained me before, I've made good use of Rinstead Pastilles. I don't know if that brand is available in the US, but there should be alternatives. They're a bit harder to hold in place when it's on the lip, but they work well.
Bonjela gel is also a good product too. Bonjela doesn't sell in the US, but there should definitely be equivalent brands.
