It sounds to me like you just irritated it. This happens a lot with belly button piercings, especially when they are pierced with a barbell instead of a ring like they should be.
Take some ibuprofen and put a warm compress on it for 10 minutes twice a day. I dont know how much you are cleaning it, but clean it only once a day to give it time to get over this little irritation. Keep an eye on it for green or yellow discharge, severe swelling or severe redness. If any of these occur, see a doctor for possibly some antibiotics.
After 6 weeks it should be stabalized enough to change the jewelry, and I would change it to a ring until it is fully healed (6-8 months) to prevent this from happening again.
