Can I move the work items from my scrum board?

Yes, you can move the work items either to the backlog or another sprint from your board. All you need to do is disable the 'Strict Scrum' option in Other Settings from your setup to either add new items to your active sprints or move the existing items from your backlog. Once you enable this settings, you can do the following:

Navigate to your Board.
Click + Item in the upper-right corner.
Select Add New Item to add a new work item to your sprint.
Select Move Existing Item to move existing work items from the backlog to your sprint.