How to reduce the drainage of a nose piercing?

Remove the piercing. Im not sure what you mean by "drainage". Hopefully you mean just clear mucous. The only defense the nose has is to make mucous. If it thinks your piercing is a problem it will respond by secreting more mucous. If your "drainage" is pus because your piercing is infected you must remove it right away.
Remove it. Your symptoms of drainage most likely represent an infection due to a foreign body (your metal). Removal and warm soaks would be an easy solution, along with topical antibiotics. Piercing represents an invasion of the tissue of the nose , presumably the soft tissue and cartilage. Chondritis or inflammation of the cartilage may be difficult to eradicate without removal of the foreign body.

Related Questions

I had a nose piercing last week every and now iam getting a clear or white colour discharge from my nose, it is continuous and im unable to stop it.

Nasal discharge. Your nose piercing and the device that you have in the piercing are an irritant to the nose and your nose is trying to get rid of it like it would if you had a foreign body in your nose. The easiest thing to do is simply remove the nose ring and give your nose some time without the metal. You could be allergic to the metal in the device, in which case changing to another metal like gold/platinum. Read more...