No, you don’t have to start over because of that. There is a technique Kent uses whenever I see a sculpting course of his. When he gets into that sort of problem, he first makes a swift and soft pass with the inflate brush, with low strength over the surface, just to accommodate the polygons, because there might not be enough resolution over that area. Then when you sculpt normally again, now that there is enough polygons in the surface, it doesn’t behave strangely.
You can also upload your file for us to take a look if you want.
