Do not know. They probably just lived with them!
Just a guess. Pioneers likely could not tell the difference between nasal polyps & other forms of rhinitis as they lacked the equipment to examine the nose. Two herbs that grow on the prairie they may have found useful are urtica dioica (stinging nettle) & plantago lanceolata (narrowleaf plantain). These herbs were known to native americans. Both are used as herbs for rhinitis.