I got my nose pierced a few weeks ago and a lump has appeared above it, it is red and was filled with liquid but it popped, what is it, what do I do?

Nose piercing. Hello, this localized inflammation was probably an infection in the adjacent area. The nose has bacteria in it and it is impossible to sterilize the inside of the nose. I am hoping and assuming you went to a reputable individual for your piercing. Since the fluid was expressed when it "popped", there is probably little to do now except for cleaning as instructed and apply an antibiotic ointment.