Why is my nose blocked after singing? Especially for high or low notes.?

Your nose often gets blocked after singing because of an anatomical phenomenon called the Valsalva maneuver. This is where you hold your breath and bear down, as if you are trying to push during labor or going to the bathroom. When this happens, your vocal cords constrict and there is a pressure build up in the chest that can be felt in other parts of the body like your nose. The increased pressure causes a narrowing of your nasal passages which could lead to congestion and blockage.

The middle range notes are usually easier on the voice than higher or lower registers because they involve less strain on your vocal cords, thus causing less tension that may result in a blocked nose. If you find yourself having trouble hitting high notes without getting congested afterwards, try warm-ups before singing; for example humming softly for 5 minutes can help loosen up any tightness around your voice box so it's not too strained when reaching for those notes.  Additionally, practicing breathing techniques such as belly breathing or diaphragmatic breathing will help relax all areas around the lungs and throat allowing more room for air flow when singing those tricky notes!