Why would I develop a bump (I think it's excess cartilage) on the tip of my nose in adulthood? How can I fix this? (Photo)

Hello and thank you for your question. Based on your
photograph, you may benefit from a tip refining rhinoplasty. Your surgeon can
accomplish this by trimming, suturing, and reshaping the cartilage in your
lower nose.   Make sure you specifically look at before and after
pictures of real patients who have had this surgery performed by your surgeon
and not just a computer animation system. The most important
aspect is to find a surgeon you are comfortable with. I recommend that you seek
consultation with a qualified board-certified plastic surgeon who can evaluate
you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Your are correct. There are two cartilages that support the tip and are called medial crura. The one on the right is protruding more and it can be trimmed.

Hello and thanks for your question and photographs.
 There is asymmetry of lower lateral Cartilage  which can be improved with cartilage modification.
please consult board certified plastic surgeon and discuss in detail.
Best of luck .
Dr Milan Doshi

the photographs demonstrate asymmetric nasal tip cartilages which are placed on stretch when smiling with thin skin.  It is important to evaluate the nasal tip cartilages at rest, not upon animation before embarking on a rhinoplasty procedure.

Our bodies change. This can be repaired with rhinoplasty. It can be the sole issue addressed if that is what you wish without major recovery time.

It is likely cartilage from your medial crura that are protruding on the side while you smile.  It can be trimmed.