Thank you for your query.
1. You seem to have a viral or allergic cold
2. Drano contains mostly sodium hydroxide which is corrosive and irritant to the delicate mucosa (lining) of the nose and throat. Even if you have inhaled some vapors, it will last only for a short time. There is no cause for worry.
3. Get your doctor to prescribe an anti-allergic and an anti-inflammatory medication along with medicated gargles to soothe the throat.