Follicle growth during IVF stimulation varies a lot from person to person, even between your own two ovaries. A size gap like this at day nine isn't unusual on its own.
Next Steps
Your fertility specialist is tracking every follicle on your scans and will decide the right next step based on the full picture, not just one reading.
Health Tips
Please don't guess retrieval timing yourself. The right day depends on how all your follicles grow over the coming scans.