Less than 1 week post op breast reduction and I somehow elbowed my nipple in my sleep (about 3 hours ago).

You are doing a great job monitoring this area! Monitoring this area for swelling, drainage, and bleeding is exactly what I would recommend. At this point, given that you haven’t noticed any changes, I doubt that the trauma to this area will cause any lasting damage but continue to monitor for the next few days. Notify your surgeon’s office if you do notice any of these changes.