"Setback" means something that interferes with or blocks progress toward a goal. It can be minor or major, but by using the word, we imply that progress toward this goal won't be stopped. Here are some examples:
"The first defeat was a setback for the invading army. They changed plans, regrouped, and prepared for their next attack."
"The new regulations are setbacks for business owners looking to expand."
"His poor performance on the university exam was a huge setback for him and his family. He will have to reconsider his goal of becoming an engineer."
I hope these are helpful. Please let me know if you still have questions =)