Indecisions, in decisions

I have reached an impasse in my novel. I have what I believe to be a good story, yet last night a new thought occurred to me. Granted, it came from the period when one is asleep, yet somewhat aware of the immediate surroundings. The noises of owls cooing outside, crickets stringing their legs together, and thoughts… Thoughts dancing wildly in the brain.
Should I plow forward with what I have? Or, stop, drop and roll… To the beginning and make the modifications to the story that invaded my thoughts at dawn? I could hold off the idea for the next novel… Oh, what WWJMD? (What Will JM Do) ;)