Fish or no?
If you have fish in the tank you can change some water. Be sure to match temperature and use the appropriate dechlorinator. Picky fish keepers try to stay closer to 20 ppm nitrate, so a water change of 25%, or even one each day, until you get to 20 ppm would be fine.
If this is a fishless cycle, using ammonia, then don't worry about that unless the nitrates get really high, like 80 or higher. I read somewhere that really high nitrates can slow the cycle, but I don't recall the numbers or source -- sorry.
A bit of salt will help fish tolerate the nitrite, 1 teaspoon to 5 gallons, on the second and third day you can repeat, for a total of 3 teaspoons per 5 gallons. Do this slow to avoid shocking the biofilter. But the water change will help tremendously and so do both.
Keep an eye on this, when nitrites go to zero you are done cycling. Then water changes keep the end product, nitrates, under control. As you add fish, this cycle may repeat if you go too fast. So go slow.
