How to handle User Story at end of sprint if users want changes?

Question

We just adopted Scrum and completed our first sprint (yeah!)

At the Sprint Review, we demoed a User Story for feature X. This feature X worked exactly how described in the User Story from initial business analysis and details we worked out during product backlog grooming and sprint planning. However, after the user saw feature X in action they wanted some tweaks (not shocking, purpose of the demo and feedback loop).

My question is:

(a) Do we consider the original user story done and create a new user story to handle the new requirements in a future sprint?

(b) Do we consider the original user story unfinished, roll into backlog with more detailed requirements that will turn into more tasks in the next sprint?

If (b), in sprint planning do we re-estimate the story point weight of the story now knowing that 90% of the work is complete? So if it was originally 5 pts it might now be 2 pts?