I noticed some swelling around the area of the top 2 stitches. That of course meant a call into the animal hospital. The surgeon's "staff member" asked me to bring him in.
After an exam by several hospital doctors, the diagnosis was swelling around the internal stitching because they could actually feel the stitch causing the problem. Since Simon is walking fine and experiencing no pain, we are supposed to "wait and see." If it's any bigger in 2 days, there'll be another trip to the hospital for a re-assessment.
Turns out there's a level of difficultly associated with getting a good shot of the area to use as a benchmark, but I did measure it (as instructed) - it's about an inch long, although it appears bigger in this photo:
