Small mirror of my shutter speed fell?

So the shutter speed inside the body of my nikon have this small mirror, and today when I wanted to take a picture I noticed there was some clicking noise so i took off the lens and discovered that the small mirror fell off, so I was wondering can I fix it myself and stick it back on the plastic parts of the shutter or I have to take to a professional?

Please take it to a professional repairer. If you can't name the parts, you can't begin to repair it.

The mirror has nothing to do with the shutter speed, and it is not the shutter either.

Your camera is broken, you can't fix it yourself. Take it to a repair shop.