It is not uncommon to see small cartilage lumps and bumps after Rhinoplasty if you look very closely at the nose. The problem of course is that larger lumps are visible and can be seen.
It is unlikely in my experience (30 years) that new cartilage will grow after a Rhinoplasty and create a new lump or bump.
The one exception is when Rhinoplasty is done on an adolescent who has not finished growing. If you have a Rhinoplasty before your facial growth is complete (ie during adolescence and before puberty is completed), new cartilage and sometimes bone growth does occur and can ruin an otherwise good Rhinoplasty result.
That is why we do not do Rhinoplasty until facial growth is complete, and puberty is passed.
Most commonly lumps and bumps after dorsal hump reduction are caused by small cartilage chips or bone chips that are left behind or when inadequate cartilage or bone removal has been achieved during Rhinoplasty.