ferret behavier

Question
i just bought my ferret two days ago and i'm confused why hes biteing the cage door in the middle of the night i cant get sleep and im worried that i may be doing something wronge


Answer
Without knowing the age and schedule of you and the ferret, I would say he is bored and isn't getting enough time out of the cage to play.  It is recommended they get 2-3 hours a day out to play in a ferret safe room with you.  Be careful as biting the cage can ruin their teeth.
Check out enrichment articles on-line by Bob Church and the Book Ferrets for Dummies by Kim Schilling.