I don't think you should have done this without confirming it was OK with your tutor. However, depending on the data, it may end up being very similar for all students and your lecturers may ignore data based similarities for this sort of assignment.
However, if part of the assignment was to collect your own data and this is discovered, it's very likely that your grade for this piece of work will be reduced. Equally, although you won't be expelled for a first offense, it means if you make a referencing mistake or have other problems in the future, you're less likely to be given benefit of the doubt.
If you've already submitted, there's not much you can do, but if you have time, try going to your lecturer's office hours and discussing the situation with her. She may say it's ok to use other data, and then you won't have to worry.