Shaving Nose Hump in a Short Time Possible?

I would agree with your surgeon.  Although it is best to wait 6 months to one year after your initial surgery, this is not the case here.  There is a specific abnormality that he feels he can correct with a minimally invasive touch up.  I think you should proceed.

Most surgeons feel comfortable performing same site surgery after a year. Sometimes this can be shortened to 6-8 months. For example if a Septoplasty was initially done, then it would be possible to safely perform a rhinoplasty 6 months later. Although both are located in the nose, there involve different tissues. The reason is to allow the surgerized area to heal and the inflammatory reaction to die down. Revision surgery is hard enough not to have further compounding issues to deal with.

If a dorsal hump persists after nasal surgery (and if that is the only residual deformity), then it is very straightforward to simply shave down the remaining bone. This can usually be accomplished through incisions on the inside of the nose. The amout of swelling and bruising is usually very limited,and the "down-time" afterwards is minimal.

After a septoplasty and rhinoplasty, you should expect to have swelling throughout your nose. You should notice some significant changes immediately after the surgery, however your final results will only be apparent after your swelling has resolved which is in 6 to 8 months after surgery.

There are several different ways to fix this deformity. If it is a mild bump, this bone & cartilage may be shaved down using only the incisions on the inside of your nose. If it is larger or there is a discrepancy between the amount of bone and cartilage, your surgeon may choose to do a component reduction which would require opening the nose for a more accurate correction.
 

It is possible to have a minor bony irregularity after Rhinoplasty surgery. As long as it is not necessary to reposition the nasal bones (which is frequently done in rhinoplasty surgery) a cast to immobilize the nose would not be necessary after your surgery. I would place tape over the nose to minimize swelling. Recovery from this swelling will probably take a couple weeks. Ask your surgeon.