Well if the white thing is on your oral tongue and visible chances are whatever is stuck in your throat (or that feeling) is likely not related. Base of tongue cancer would cause that feeling, but an oral tongue cancer, not so much, unless it's advanced and has spread, and usually that involves lymphnodes at that point. Not to say that whatever is on your tongue isn't cancer (though chances are it's not) but that stuck feeling may be related to stress, or as connie said acid reflux, or something else.

Base of tongue cancer is generally only visible with a scope, as it's down the back of your throat and not always but often has a different cause than oral tongue cancer.

I know I probably muddied the water here, but I guess I'm just trying to say not to freak out - as several others have said, what is on your tongue could be caused by several things.

take care and fingers crossed you're clear.