Tragus piercing 20 days old is infected. think there is puss in it. what do i do?

Infection?: If you think you have an infection, you should be seen by a doctor before it gets worse.

Remove piercing: Clean site with peroxide, use topical antibiotic, and if red/tender/swollen beyond size of a nickel--needs seen by Dr and likely oral antibiotic to address infection of cartilage. Can always attempt re-piercing once fully healed.