I've had my offcentre-labret for over 4 months now.
It has healed perfectly, though lately it sometimes randomly stings as if there's a splinter inside my piercing.
I have already tried taking my piercing out and cleaning it thoroughly, to no avail.
No, it is not infected, red, swollen or leaking pus.
There's a few things that come to my mind, could be a metal allergy or some dry lymph could have gotten lodged inside.
I would almost say there could be knicks on the jewelry itself causing it but that doesn't normally happen unless you remove the jewelry often and not 4 months after getting it done.
If it continues it could be worth a shot to get some new jewelry made of a different metal. Then see what happens from there.