I think I would contact the seller and send them a photo. If they are reputable, they will probably send you a replacement, and probable also let you keep the damaged bulb.
If it were me, I would try to to pull off the outer layer of the bulb and see if the next layer is good. If that layer is too bad, I would take a sterile knife and cut out the bad part - maybe dab the area with a water/peroxide mix. Then let the bulb dry out out for few days. Then coat it with cinnamon and replant it. Is that a bulbette I see? If so, it will probably continue to grow. Keep us updated - will be very interested in seeing how it does - I would not give up on it yet.
