tobacco is known to give sinus infections when smoke is inhaled or exhaled through the nose because the nicotine paralyzes mucous membranes, making the nose dry and prone to virii and bacteria.

if you dont smoke cigs i doubt its from the weed.

being diagnosed with chronic sinusitis multiple times, i can tell you that refraining from blowing or inhaling any smoke from your nose will help the situation, and possibly prevent it.

the post above me had a good point too.