loose filter thread ring on summicron m 35mm
I bumped the lens hood on my cron (attached to an M) against a swinging door. All seemed OK, except that I noticed the filter thread ring to which the hood is attached has gotten loose and now rotates from F2 marker to f16. The aperture ring, though, is solid, clicks as before and works well, and nothing else seems to have been affected.
Any ideas, colleagues? A must trip to the repair shop? or is there a simpler solution?
Thank you in advance for your response. Here is an image as an illustration. As you can see, on the left, the aperture ring is on f2 and the white notch on the filter thread ring is opposite it; on the right, though, the filter thread ring with its' white notch has moved moved to f8, while the aperture has not changed.