You can do this, you have a add a USER ID field to your tracker, and the edit the tracker's properties and make sure the Item creator can modify his items? option is checked.
You also have to set all the fields in the tracker under the field is hidden option to visible by admin and creator only, so that other users can't see the fields.
I think that's the basics of it, it gets a bit more involved if you want groups of users to share information but that is possible too.
Check out the Tracker documentation, it should give you all the information you need.