I believe that God respects the individual not the sport. If your intent is to win fairly and humbly then all is well with Him. Boxing is a violent sport but so is football and rugby. Would you pose the same question regarding those sports?

You are not boxing out of anger or hate, correct? Do not let pride take over your soul and understand that there is no shame in losing to another boxer. Do not wish your opponent harm and understand that God loves him just as much as He loves you.

Outside the ring their is no reason to harm another man with your fists. Keep that in mind as well...

The real answer is to pray on it for yourself. You have a direct line to God ask him for yourself, and wait patiently for His answer. It will come at exactly the right time.