What is a dangerous level of nitrite in an aquarium?

I am doing a cycle with fish, and the Ammonia has dropped down near 0 ppm, the Nitrate has risen to around 10 ppm, but the Nitrite is stuck around 5 ppm. Is this a very dangerous level for Nitrite? It has been this high for a week now and I have done two water changes, but I need to know if I should be doing changes daily?