Invisalign causing isolated tooth sensitivity?

After 8 months of Invisalign regular treatment, I started refinements 2 weeks ago. Since then, I have a growing sensitivity in one tooth, #3 (w/7 year old crown). My dentist says I'm probably clenching or grinding and it'll go away eventually. I just had a 6-month checkup with full x-rays, with no issues. No cold or hot sensitivity. It's OK to eat on, though some foods cause more sensitivity. This is the only tooth bothering me. Anything to stress over? I think I do clench, unfortunately.