I have this itchy red pus looking bump on my lower back above butt crack. It's not painful just very itchy, most part of the day it wasn't itchy.?

Abscess cyst. What you are describing is most likely a congenital condition known as a pilonidal cyst. It is not a dangerous condition, but should be fullly evaluated by a physician and then treated appropriately. It may require excision or just incision and drainage and obliteration of the cyst walls. You should be evaluated by a physician to determine the exact diagnosis.
Be checked. It is difficult to know if this is a reaction to a substance or infection. Reactions are itchy but pus indicates infection. The treatment for each is different. Be seen. In the meantime keep the area well irrigated and clean. All the best.