When did you first notice this? How long has it been there? Has it changed since you first noticed it? How is your general health - do you have high blood pressure or diabetes? Are these conditions (if present) well controlled?
I would definitely recommend that you see an optometrist or ophthalmologist to take a look. The fact that it is central in your vision and you cannot see through it makes me worry that it is quite serious! It could be something on the anterior of your eye (the cornea or lens) or posterior, such as macula oedema.
Definitely have this checked by specialist. After noticing this prob with my left eye a couple of years ago, I required a vitreo-retinal peel. The macula was being lifted, and the retina was threatened. Last week I required same surgery on right eye. Successful, and still recovering. Had it been ignored, a macular hole would have developed.