Stop Working And Add The Incomplete Feature Back Into The Backlog. Stop Working But Ask The Assigned Resource To Complete The Feature While You Plan The Next Iteration.
The possible negative consequence if you don't create a storyboard is that it will not allow the client to navigate around the storyboard as if it is the final site. This helps them get a much better feel of how things fit together. I hope my answer has come to your help. God bless and have a nice day ahead!