Like many people who are facing new symptoms after a successful spine surgery, you have answered your own question. Yes, you should make a follow-up appointment with the surgeon as soon as possible. It may be nothing and the symptoms could go away on their own. But delayed post-operative problems can develop. The sooner the symptoms are diagnosed and treated, the better your outcomes.
The surgeon will likely start with an X-ray to see if there are any obvious signs of trouble. The implant may have shifted causing locally increased stress forces. The result could be a stress fracture in the bones around the device. Or there could be an entirely new and different problem starting to develop. Finally, as you may be hoping — perhaps this is a temporary situation that will go away without doing anything.
The X-stop device works well to distract and separate two vertebrae in the lumbar spine. And that distraction is enough to take pressure off the spinal nerve roots. Recurrence of symptoms is a signal that something may be irritating or compressing the spinal nerve roots.
Follow your own intuition (gut feeling) and make a phone call to your surgeon today.