Most assignments prevent you from entering answers after the due date. But your instructor may choose to allow late submissions on an assignment. If late submissions are allowed, you will see a note in the Assignment Information in the Resources sidebar of the activity.
Additionally, you will see an icon on the main course page next to any past-due activity that allows you to continue working.
Any deductions for lateness will be applied to the additional points you earn after the due date. Any points that you earned before the due date are locked in. In other words, if you are able to click Check Answer, it will never hurt your score to do so. It can only increase your score to keep trying.