Help! I think something went in to my piercing?

Background: I have had my tongue ring for about 10yrs now. I wear acrylic beads on a metal bar. I haven't had any problems with it for years.

Then...
About a week ago, after (not during) eating it suddenly started hurting a lot! I took it out and rinsed it the discomfort was so significant. I appeared that something had gone in the hole with the barbell and irritated it. This has never happened before! I have been using salt water and mouth wash rinses for the last few days and my tongue continues to be tender as though I had just got it pierced...and tonight when I took it out to try and see if it just needed cleaning I noticed the centre of the piercing looks dark...
Wondering if anyone has any idea what might have happened or suggestions to make it stop hurting?
Cheers.
Thanks