Sinceyou do not say what happened, it is difficult to answer the question. If you had something large in your vagina (like a penis or a sex toy) it will likely tear. There can be a few drops of blood when it tears. You can also tear it with a finger if you are not careful.
If your hymen is important, your doctor can tell you what is going on. You can also take a mirror and look. If you do not know what it looked like before, it can however be difficult to recognize.