What Causes Hard Knot At The Center Of Piercing On Tongue?

I've had my tongue pierced for about 5 years now and it hasnt given me a problem until the past few days. I woke up one morning and it was slightly painful and I was messin with my piercing a lil bit. now i've noticed its swollen around the piercing and when i take it out I felt my tongue top and bottom and it feels like theres like a hard pea sized pebble directly in the are of the piercing. Is this irritated scar tissue or what?