Hi there,
Again, I’m not an expert, but I would be surprised if the yoga is actually exacerbating the problem. It should have a ‘cleansing effect’ (flushing stuff out), if anything.
I can get quite congested and I have found that using a saline nasal spray before class really helps (my product says ‘sea water spray’). It flushes out the sinuses quite effectively which relieves the pressure, opening up the nasal passages for further cleansing during class.
Perhaps that is something to try? If you have an infection already… well that’s a different story.