...Swelling can be a sign of different things. I typically begin to swell before I start healing. Some users experience swelling when they are having an allergic reaction to the cream.
I would suggest you reach out to your doctor/send pictures if possible to get their advice. For the most part, I don't stop applying cream until the area becomes scabbed over and weeps clear fluid. That is usually a sign you have reached the erosion phase and the cream has done all it is going to do.
I am including an article that may answer some of your questions.
https://skincancer.net/life-with-skin-cancer/efudex-cream-how-long
I am wishing you all the best as you continue toward healing! Please keep us updated on your progress! We are here for you!
April, SkinCancer.net, Moderator