Palatal Sinus Tract Developing After Implant Placement: Thoughts?

Dr. A. asks:
I placed an immediate implant after extracting the maxillary left first premolar (#12), that had previously received root canal treatment. The tooth was asymptomatic prior to extraction, and there were no signs of infection clinically and radiographically. I prepared an osteotomy, prior to placing the implant, and I probed the osteotomy site to make sure all the walls were intact. I placed the implant, had excellent initial stability, cover screw, sutures,and so on. Everything went beautifully.

Patient called 4 days post-operative saying she has swelling. She came in the next day, and she presented with a palatal swelling with a sinus tract extending almost to the palatal suture. The swelling had decreased by the seventh day. I will see her next week, and if the palatal sinus tract has not resolved, I will flap to see where it directly is coming from.

My question is, I felt for the wall of my osteotomy and they were completely sold and intact, and I even had a look on the palatal side after implant placement, and no perforation seemed to be present. Can a palatal sinus tract develop so quickly after implant placement if a perforation did occur? Can it be something else? Can I do anything else other then taking the implant out, socket graft, and return at a later date?