Today I have closed the Sprint.I have tried to see burn down chart and found that it shows scope change at couple of place. After analysis we found that if we log any defect while testing of user story it shows as scope change. In reality it is not scope change, it is part of user story. As per our DOD, testing/defect fixing should be complete within sprint.
Please let me know if you have any guideline for handling the defect of user story in active sprint.