Well I hate to say it, but if the data was really important to you then you should have made backups first. This is exactly the reason we try to discourage dual boots, as data loss is always a possibility
You could try the program testdisk to recover your data.Testdisk is a terminal based data recovery software. There is plenty of documentation that is already existing for the testdisk program. As our forum is not a site dedicated to data recovery you're kind of on your own here as far as recovering data
Always remeber that every change you make to your drive lessens the possibility of data recovery.
Good luck.