@ddljohn-- You can skip the ulceration stage with the use of antiviral creams, medications or some cold sore cures and remedies. If you kill the virus, the cold sore won't be able to turn into an ulcer. I accomplished this once with the use of salt. I applied salt several times a day for as long as I could hold it when my lip became swollen (second stage). It never formed a blister. It just scabbed over.
I think medications like valacyclovir and supplements like l-lysine can do this too. I haven't tried them though, so I can't say for sure.
Why don't you ask your doctor? I'm sure that he would have some recommendations, especially if you get cold sores frequently.