If nose is straight after fracture-- but there is a bump - is closed nasal reduction w/general anesthesia necessary? (photo)

If there has been no change in the contour of the nose on frontal view (shift, crooked etc), a closed reduction is not indicated - at least in my opinion. A new or larger bump will likely not improve with the reduction. Wait for all the swelling to have subsided (3 to 6 months). At this point, the nose should be assessed and a possible rhinoplasty considered. 

As you noted, your nose looks straight to you.  There is no need for a closed reduction of your nose.  The nasal bump you have should be allowed to settle and fully soften, which takes 4-6 months and then reevaluated to see if the nasal contour has returned to its pre injury shape.  If it has, nothing further needs to be done.  If a bump remains, you may wish to improve that contour by a rhinoplasty.  Patiente is best for now.

The bump is not going to get better after closed nasal fracture reduction. That operation is designed to help truly crooked noses in the immediate post-injury period with any incisions or significant surgery. It's a quick operation that moves nasal bones back to being straight. It won't take care of the bump. I would wait at least 6 weeks to see if the bump will come down. Good luck!