I think first egg is a surprise not only to us but to the pullet. They have instinct to lay, but don't know yet what is going on until they have laid an egg. One of mine laid her first egg after sitting in a nest, came out of coop and laid it while running down the ramp and another laid her fist egg while drinking at the water fount.
Your broken egg might have been accidental like mine did. Or someone pecked it to check it out and it broke. They often do push them around in the nests.
But you don't want them to want to eat their eggs. Make sure the nest has something soft in it. Try to check for eggs and collect frequently for a while to try to prevent opportunity. If they do show tendency to peck the eggs, some folks recommend placing golf balls or hard fake eggs, like marble ones, so they learn not to break eggs.