You sure can! If you’ve settled on a winning design before the contest is finished, you can end your contest at any time by declaring a winner. Your contest will end immediately, and you will enter the Design Handover stage with your winning designer.
If you intend to run your design contest for just 1, 2, or 3 days instead of the normal 7, you can purchase a fast-tracked contest during the launch process (please note: this option isn’t available on Website, Mobile App, or Logo & Hosted Website contests).