The mere filing of a complaint in court does not provide notice on the defendant, nor does it confer the court's jurisdiction over the defendant. In order for that to happen the defendant must be properly served with both the complaint and a duly issued summons from the court.
Not necessarily. If your context is a court case, generally once filed the party initiating the lawsuit will arrange to have it served on the other party. There could be a reason not to seek service right away, but generally it will take place in short order unless the other party can not be easily located.
If your context is work, a supervisor might consider the complaint petty and just note it and not take any further action.