Belly button piercing infection?

I noticed recently that when I touched the skin of my belly button piercing that it hurt. It doesn't hurt or anything if I leave it alone. I have had my piercing for at least four going on five years. I have never had an issue before. So, I'm unsure if this is an infection or not? Anyway, I took my piercing out to inspect further and found that it was the bottom, most inner hole to the belly button that hurt and it was slightly red (but this could be from messing with it). I also noticed a sore lump had developed in it. It hurt to press on it. Almost like it was a build up. There was only a very very tiny amount of fluid that has come out of the piercing. And I would describe it as being clear to slightly gray, but I have seen no more as of yet. So, I let the piercing sit out for a little bit and found that the bottom hole actually looked like it was protruding. Very strange. But still no pain normally. I read a few infection articles, but my symptoms don't seem to really match and from their advice I but back in the jewelry. Which did end up hurting a bit almost like i was having to reopen it. I have soaked the piercing in hot water and salt, this seemed to help a bit with the lump. But I'm still unsure if this is a true infection or if it may be something like a build up of junk. Has anyone encountered a situation like this? Any suggestions?