Is lumpy cartilage after an open rhinoplasty normal?

Very good question.  The lumps may be a result of cartilage remnants or edges and it is uncertain whether these areas will resorb or stay longterm.  The uncertainty comes because only your surgeon knows the origin of those uneven areas.  In most cases, however, they resorb.

Its hard to tell at this moment. Your nose is swollen and so masks the underlying structural changes. The lump could be cartilage. Sometimes its possible to tell even at this early stage. But this would require an experienced hand. Even though the nose is swollen, it should be symmetric. If its not, then you may in fact have a problem. The degree of which will become clear in time.

At 3 months, you should be seeing basically a slightly swollen version of the end result. There is still some swelling present at three months and some scar tissue will continue to soften. If there is quite a bit of irregularity at this time you may need a revision. Unfortunately, you need to wait until one year from surgery before I would recommend revision rhinoplasty. Things will continue to evolve and your plastic surgery does not want to be working on a moving target. Hopefully, this will simply improve over the next 9 months and you will be thrilled with the results.