You have a BIG problem.
This happens when the system was shut down suddenly (in your case by power cutoff). Usually this goes without problems, just a quick file system check and it's all right then. But in your case the system was unable to boot again after a node in the file system was lost when the power cut off. Therefore the file system check couldn't complete. The system dumped you to a shell presuming you would fix the problem yourself. The shell is very
limited, only enough to fix the file system error. I'm afraid, there is not much to do in this situation, but you could try to fix the error.
If the check starts properly, it would begin asking you a lot of yes-or-no-questions. You should answer the default, which is written on the right like: .......................[y] (the default is y).
When the check is done your system will work without problems. Try it, if it fails come back here
By the way, your question: No, the shell you were dumped to is the shell you have to work in, you can't use your default login here.
Hope this helps