How to heal an unwanted piercing?

When I was younger I had a lot of piercings, I ended up with 4 belly button rings. It was really cute when I was younger but now that I'm older I want to take two out and leave two. The problem is that they just won't close. I've had them out for probably two years or longer and they won't close. One of them even has a hardness to it. I keep trying to squeeze it out but it doesn't seem to help, probably counter productive actually. Is there anyway to get them to close permanently? Even if I have to get some sort of procedure done. I'm willing to do whatever I have to to get rid of these! Thanks!