You are still pretty early after rhinplasty, but that said, the bump is not subtle. Possibilities include swelling around cartilage grafts, a misplaced cartilage graft, or a small hematoma (bleeding) the accumulated under the skin. It is best to discuss this with your surgeon as he/she has the best idea of what maneuvers and cartilage grafts (if any) were used during your rhinoplasty. Some surgeons use PDS plate (a slowly absorbable material) to help guide cartilage healing, and this can create a significant amount of swelling as the body breaks it down. Other surgeons use artificial grafts, like silicone, which can accumulate fluid around them or get infected. Again, your surgeon will know the most likely cause.
If it is felt that the swelling is most likely due to swelling around cartilage grafts, then 5-fluorouracil (5-FU) or steroid injections can sometimes help to speed recovery.
Best of luck.