Nsor set the Estádio Municipal José Santos Pinto ablaze with his terrific display for Viseu on Friday.
The former Metz striker shot his side into the lead in the 17th minute with a superb strike before Portuguese defender Bura Miguel Ângelo Marques doubled their advantage in the 25th minute.
Sporting Covilha reduced the deficit courtesy Reinaldo Mandava in the 61st minute.
But Nsor quenched the home side's fire to draw level with a 73rd minute goal to hand Viseu a 3-1 win.
Nsor was named the man of the match following his scintillating performance.
Viseu sit 6th on the table with 50 points.