Concerning English er Spaniel skin problem?

I have an English er Spaniel, 1,5 years old, I discovered a little spot near right lip, which got ulcerated and vet just removed it and put on some iodine..After a week I noticed that there appeared two new crusty spots just near the last one...The vet recommended balsam. What should I do? Should I just follow the vet advice or take dog to another vet for skin test?