When Can I Go Back to Bikram Yoga After Rhinoplasty?

As you know this can Bikram can generate alot of heat which can contribute to nasal swelling. While your rhinoplasty should be able to tolerate this at 6 weeks, you may find it uncomfortable due to nasal congestion with feelings of sinus pressure. Any positions which force you to strain or bear down against a closed glottis (Valsalva) maneuver) will also produce increased swelling in the head and neck area.
Alternatively, high humidity conditions can promote nasal drainage and evacuation such as a warm shower.
This is a unique question and one I have never been asked. I would definitley consult with your rhinoplasty surgeon. In any event, I would start off extremely slowly and proceed from there with gradual and increasing exposure to these conditions.

The only concern is if you bump your nose. If yoga avoids any contact then you will be fine. I like the heat and humidity for your nose.
You can help your nose by putting a saline spray or gel up your nose prior to your exercise.
Best of Luck.