There is almost no bone stress injuries that allows an athlete to return to sport (particularly running) in 4-6 weeks. Others have suggested he had a "tibial stress reaction". If that is the case, it would likely be grade one or two. But this bone is weight bearing, and is therefore considered high risk. The incidence of recurrence in tibia is 20% among track athletes, and largely due to returning to run too soon. The average return to sport time with high risk grade 1-2 injury is 12-13 weeks. And that is the time to begin running again, not to go and race indoor. JWH is absolutely correct that doing this race is foolish. He has so much more to lose than gain. Needing to start the clock again in January would be make it very difficult to have much of a junior season.
I am a fan of this kid and have watched him run since elementary school. I hope he doesn't feel obliged to race because he made some bold statements about his goal time. A DNS would be just fine. Nobody will remember in April.