Why does the upper part of my nose, in between my eyes, aches sometimes during nasal irrigation?

This is usually caused by rhino-sinusitis. Since the sinus ostium is obstructed and resists the saline from passing through, the flow would then pressures the para-nasal sinuses and makes you feel soreness and pain. In this case, we suggest you to pause irrigation, and use hot towel to compress the aching area; resume irrigation after 2 ~ 4 hours. If aching happens during each irrigation, we suggest you to consult your doctor for nasal cavity and para-nasal sinuses check-up.