So I've had my belly button pierced for about 4 months. I haven't had any pain with it besides when I first got it. I just recently changed the ring and it's red like when I first for it pierced. Like I said it doesn't hurt but it's really red at the top.

Start using salt water rinse, keep the area clean. You will notice redness decreasing. The skin has been irritated by the change in ring.

Like the piercing stuff or can I just mix water and salt?

Mix water and salt. Warm water, about 4 oz. and tsp of salt