Can piercing your cartilage with a gun hurt you It was about 4 days ago and it still hurts pretty bad..and no infection. so what do you think?

Go see an actual piercer to have them check it out. Guns use a lot of pressure and can cause a lot of bruising and unnecessary trauma so it'll hurt longer than if you had gotten it done with a needle. Using a gun on cartilage is a terrible idea because you could have shattered the cartilage and disfigured your ear. Chances are that the stud is too short to allow for swelling so go to a piercer and have them give you proper jewelry and check the area for infection. Definitely dont use a gun for any other piercings ever again.