I was on site for my new boy's PPE and had a similar issue. The horse had only been barefoot in front for about 3 weeks..owner had pulled shoes to avoid him possibly losing them while she was out of town at shows; he had been barefoot behind for nearly 2 years. His feet were short and chipped up in front when I first saw him. At the time of the PPE, he tested positive to hoof testers in both front but it was along the outside wall. On the trot out, on hard ground as it turned out, he was ouchy in the front left. Flexes were clean and x-rays were also clean. Vet said the same thing (and my vet concurred when I sent the report and radiographs) that the feet were just tender. The horse had glue on shoes placed in front and regular shoes behind about two weeks ago and he is fine. The feet are already growing out.
Have radiographs taken..it is the only way to tell if the ouchiness is internal structure (navicular or some other issue) or if it is hoof condition.