Hi -
This isn't a symptom of HIV. This long after exposure, you are beyond the point of developing ARS, and if you did, you'd be VERY ill, not just a little twinge in your throat here and there.
If you have allergies, live/work in a dusty/dry/damp/moldy area, then that could account for the occasional sore throat. It could also be a heightened body awareness since you are anxious about having HIV. If it lingers or gets worse, get your doctor to take a look.