First be sure if you are pregnant or not by taking the pregnancy test. If it is a cramp then it is normal in early pregnancy. If it is some pain then you have to go to doctor for check up. There are many different things you would experience if you are pregnant. You don't need to be worried for everyone. It may or may not be harmful. Just follow the guidelines of your doctor.
Get a pregnancy test and see a doctor. This may simply be normal aches and pains associated with a new pregnancy but also could be a very serious problem such as a tubal pregnancy.