Do not whine
If you are merely in pain, deal with it and keep fighting. Do not show pain to opponents. It gives them confidence and shows them where to strike next. It also lets the judges know your opponent got in with the technique. If you are injured, it up to you and your instructor/coach as to whether you should continue. For an obvious injury, the referee may make the decision for you. You do not see animals whining during a fight, they finish the fight and lick their wounds once it is over.
Stick to basics unless you are overwhelmingly better than the opponent. Tournament sparring is not the place to impress spectators with your expertise. Your only goal is to score more points on your opponents than they may score on you.
In Olympic style sparring, you must have power. If you do not have power, then you might as well forget about scoring. You have to strike your opponent with enough force to "move" them. Without power, you cannot score even with a technique that makes contact. To conserve energy, save kicks for the ones you want to score with. Add power to kicks by pivoting and using the hips. Do not stop kicks at the chest protector. This will probably make a loud sound but it will not score a point, since it is not a "shuttering" blow. Kick through your opponent.