My so did exactly this 1 year ago. He was tumbling on floor and felt something while punching front on a tumble pass. No swelling just 'odd' feeling. It hurt to bend his knee and when he touched the kneecap.
We did not expect a fracture! It was a sleeve fracture where a small chip of bone tears away with some cartilage along the bottom of the knee-cap.
Sorry to say that this is VERY serious because if you push it, you can end up really messing up the knee cap which will require surgery.....an injury that can heal in 3-4 weeks, with TOTAL immobilization, can easily turn into being out for 6 months.
Take it seriously....these are kids, they have lots of time for advancing in this sport. There is no reason to compromise his health, and ultimately his staying in the sport for one meet or season.
besides, al at least with a long leg cylinder cast, you can still do quite a bit of conditioning, and stretching....he could be back in the gym at 100% in a month, or he can just live with the pain and limitations for 4-6 months.....
Sorry, and good luck.....tell him to hang in there and remind him that good athletes always come back from injuries!