How Long Should I Wait After my Septorhinoplasty to Have Botox Injections?

I would wait about 4-6 weeks. Before this I would be concerned that the Botox might not stay where it's put. By six weeks, even though there is still swelling that has to resolve, things are pretty much locked in. Ask your surgeon.

Until the swelling goes down, it will be difficult for your injecting physician to appreciate the degree of filler or Botox that would be necessary and where to place it. I recommend that you discuss this with your physician and then plan treatment in another four weeks to achieve a more optimal result,

Botox after rhinoplasty should not result in any complications as long as the majority of the swelling has gone down.  One month should be plenty of time.