Is my silicone implant crooked? Is filler in the nostril rim an option? Is a revision rhinoplasty the only way to fix?

You do have a slightly asymmetric nasal implant.  This could be dues to asymmetric placing, shifting (as opposed to your own cartilage, implants can shift over time), preexisting facial asymmetry.  Fillers in the nostrils are a bad idea and can lead to skin/tissue loss.  The ala (nostrils) can be adjusted with cartilage grafts.

Hello and thank you for your question and sharing your photos. An in-person consultation is needed to give you a definitive advice. Generally speaking, I avoid placing silicone implants in the nose, as they will invariably cause problems. I would seek consultation with a board-certified plastic surgeon
for a full evaluation and advice. Best,
Pejman Aflaki, M.D.                                            
Johns
Hopkins-trained double board-certified plastic surgeon

If have  a minimal asymmetry. It is not worth the risk of a revision surgery if you plan to keep silicone. 

It's difficult  to tell if your silicone implant has shifted, or there's just facial and nasal asymmetry. An in-person examination is going to be required to make a determination about the risk versus reward ratio taking it out and placing it in a more straight position. In our practice, we do not recommend fillers placed in the nose, and especially in the nasal tip because of it's only temporary, is not FDA approved for that application can have significant complications such as skin necrosis. A composite skin/cartilage graft harvested from the ear can accomplish bringing the nostril rims downward

Silicone implants for the nose are no longer the gold standard. The gold standard utilizes  organ donated rib cartilage that can be diced and placed into a burrito shape. This graft is highly consistent and provides ideal dorsal onlay grafting that is stable. Eventually, you will need to remove this implant as it will extrude. Please consider a consultation with a nasal revision specialist.