Is 14 too old to become a champion show jumper?

While the break in your riding may have set you back a little, you can absolutely still go pro. Just ride as often as you can and as many horses as you can. Sign up for some local shows to gain experience before moving up to ranked shows. Work hard to develop your skills and fine-tune your technique. Find a good riding school that is competitive and can work with you to move up as a rider.