Traumatized piercing or infection?

Is it septum piercing or nostril? How fresh is piercing?

You can head to pharmacy and ask what they recommend in the morning. As of now(1.30am) you can boil some water, add some salt(1/4 teaspoon of salt to 1cup of water), mix, let ot cool and when its warm/cool, you can use cotton swabs(not sterile) or ideally sterile gauze soaked in salty solution, to clean piercing.

But if pus is coming out, see the doctor as you may need oral antibiotics.

Nostril. About 20 days. It seemed liked it had pus in it 2 days ago, but I think it has drained now. It's not as swollen anymore. Do I still need antibiotics?

The answer to 'do I still need antibiotics' can be only given by qualified, trained medical professional=Doctor/GP. After seeing you in person or having seen photos of your piercing/infection. Nobody will give you answer to that over internet and whoever will, they lie. There is NO shame to go to Dr even if you feel that somehow, its your own fault(infection). It will be shame, if it gets worse and you seek no medical attention. I mean, at the end of the day its your decision. Your call. Do not trust online strangers. Any regrets, issues later-will be on you.

As have been dealing recently with skin issue of my own(I had it previously, so I knew what to expect), I waited circa 2-3weeks before contacting GP. I tried previous route of care and it did not help, it only got worse. Now, bcuz wounds are bigger I will possibly have more scarring and its my own fault. So whatever you decide, is on you. If its your first piercing and you do not know normal from not normal, see dr. Maybe they will say its nothing and you will be happy to move on.