Infection at old piercing site (gross details inside)?

I was sitting down watching a movie when, out of nowhere, I had the urge to itch near my belly button. When I went to itch the spot, I felt a hard lump. When I examined it to figure out what the heck the lump might be, the very slight pushing of my fingers made gunk pop out from my very old belly button piercing. It’s been years (something like 12) since I’ve had any jewelry in it. I had an operation and had to take the jewelry out and afterward I just decided that I didn’t want it anymore, so I left it out. I checked it regularly to make sure it was closing, cleaned it on a regular basis to make sure nothing got in there when it was closing, etc.

Other than a slight scar that made it appear as if I still had a piercing, I thought it had completely closed. But clearly, if stuff like that came out, it didn’t. How can I tell if this is an infection (why would it have itched, otherwise?) or if it’s just a gross buildup of gunk that I can take care of on my own?

I cleaned it out and put some neosporin on it since it’s antibacterial, but would something like a sea salt soak be better? I was thinking it might, just to dry out whatever might be left in there. If I don’t have sea salt, can I just dissolve regular table salt in water?