What to do if i have 2 infected cartilage piercings. how do i stop the infection?

Aggressively: Infections are never trivial and need to be dealt with as soon as possible. Any foreign body (such as the piercing jewelry) provide a safe haven for the infecting organism that your body's infection fighting defenses can't reach. If truly infected, you need to remove the hardware, drain any abscess, use warm compresses, and probably start an antibiotic so you should see a doctor right away.