9 months post-op rhinoplasty and my tip is still square-like and not defined. Should I be considering a 2nd rhinoplasty? (Photo)

Hello! It is somewhat difficult to answer the question without knowing what your nose looked like prior to rhinoplasty and exactly what was done, but I advise my patients to wait a full year. Swelling after rhinoplasty can persist for some time. You could consider steroid injections understanding that the risks of hypopigmentation and excessive thinning are possible. If you opt for steroids that can be done at any time. Otherwise I would recommend talking to your surgeon at the 12 month mark about your expectations and options. Good luck!

In the last couple of months of the year, the tip often changes some, but not gigantically.Besides working on the tip, though, doesn't it seem that the area above the tip is still wide? At least from the frontal photo you posted, I was wondering whether that area would look too big if the tip were brought into better form.
The woman in the short video that I posted with this answer had the tip of her nose modified in a revision operation.
Be sure to read the section in the "Learn more" link on how to stay out of trouble while searching for a rhinoplasty surgeon, and how to tell whether your previous surgeon should be performing your revision. Rhinoplasty is an exquisitely difficult operation to get right, and you should only have surgery if you are able to make yourself very confident in your surgeon's skills. 
Finally, I usually make computer morphs when I'm answering a RealSelf question, to show the changes that are possible for your nose with a rhinoplasty. But unfortunately the photos you submitted aren't good enough for making morphs. At the *very* bottom of the "Learn more" page is a link to instructions on taking photos that are more comprehensive and useful for online consultations like this, in case you'd like a more complete evaluation.

I would first recommend a trial of monthly steroid shots.  Some patients have more issues with swelling than others, and time alone is not enough to resolve the swelling. Sometimes revisional surgery is necessary to deal with swelling, with an appropriate amount of cartilage resected.  If you do not respond to steroid shots, then after at least twelve months from your original surgery, revisional surgery can be considered.