What is causing the dent in my forehead? How can I fix it? (Photo)

Most facial depressions or deficiencies can be augmented or filled with facial fillers. While you are correct in that most people probably don't notice anything about your forehead, filling in the area with a temporary filler is a great option. Many different types of fillers would work well in that area, and are a relatively simple and quick fix.
All the best,

Thank you for the photos and your questions. I don't think this is a dent, per se. It seems to me that you have some thickening or hypertrophy of the corrugator muscles. These sit under the medial part of the eyebrows and pull the eybrows and forehead down and in. Relaxing the muscles with Botox (15-20 units should suffice for a 20 year old woman) should help to smooth and flatten the area. Best of luck and take care!

The appearance of a dent in your forehead  is caused by very large supra orbital bones. These bumps create a depression above which looks like a dent. The treatment for this is removing the supra orbital ridges through a hairline incision which will Not result  in the and visible scar.  This is a technique  I have used on transgender patients for more than 35 years. Look at the results on several websites and especially look at the resultant hairline. 

One thing to consider that no one has mentioned yet is to start with botox. I don't have the advantage of seeing you in person of course, but the "dent" is just above two areas of fullness which as one doctor pointed out could be due to prominence of the bones (supraorbital ridges). However, I have also seen many cases where this is due to muscle hypertrophy and specifically - the corrugator mucles. Using botox in these muscles will flatten them, especially with repeat use. 

can easily be managed with fillers or fat grafting, assuming that the adjacent areas are acceptable to you.  If you aren't sure about whether you will like the fuller look, then go with fillers as they eventually go away whereas the fat grafting could be permanent.

The central forehead dent is the natural result of how your brow bone developed. This is more commonly seen in men than women. The treatment options are to either fill in the dent or reduce the projection of the brow bones. The choice depends on what you want your forehead shape to look like after and can be evaluated before surgery with computer imaging.

The defect in your forehead can be easily managed with fillers or fat grafting, assuming that the adjacent areas are acceptable to you. Consult with a board certified plastic surgeon who is highly experienced to discuss your options and expectations.

you can simply fill the hollow area with some HA fillers. This doesnt require an operation, will camouflage the hollow and can be removed if you don't like it. In that location expect at least 2-4 years duration with restylane. Not perfect but that's what I would do on me.  PS Don't sit under lights. Sit facing them