I had my belly button pierced April of this year.
Recently I bought new jewelry and changed it out (I have changed it out before)
I did change it out each day for 2 days and now I have a weird boil/bump over my piercing hole.
I took out the jewelry because it was bleeding and I wanted to clean it and the boil is over the hole and I can't get the jewelry back in now. I've tried and it hurts when I try to push through it.
I have been doing warm water + salt soaks for three days now.
Anybody know what it is?

Here's a picture:
http://i46.tinypic.com/15drlz.jpg

If you can get to a professional piercer ASAP they may be able to use an insertion taper to open the channel and reinsert jewelry. It has surely shrunk up too much for you to just put your jewelry back in yourself. I suggest NOT changing jewelry at all until at least 6 months have passed (unless the jewelry is of poor quality or fit).

I saw the photo and I wondered, was the piercing on the interior of your navel, or on the lip of tissue above it? If the former, I would not suggest you try to get the jewelry reinserted.

It looks somewhat like a "localized piercing pimple (http://piercingbible.com/troubleshooting#Localized_Piercing_Pimple)" and you can learn about those on my site, along with how to deal with them.

I would suggest continuing saline soaks (http://piercingbible.com/saline-soaks), in case that needs to drain.