I took my iPhone 4 apart and now the display isn't working so I was trying to replace the front of my phone. I didn't need a new LED display because just the top corner of the glass was chipped.

Well, I took the phone apart shortly to find out that it's impossible to remove the LED from the front glass so I just put the phone back together the way it was.

Now when I turn the phone on, it just sits with a black glow. However, it does respond to the power button, but it displays no color other than black. So you either get a matted black (off) or a glowing black (on).

Has anyone ever run into this before? Thanks.
I concur with Jan's suggestion, and direct you to iFixit's Installing iPhone 4 Display Assembly. Perhaps if you repeat the procedure, carefully following the instructions in the guide, you can restore the display functionality.

I would also add, at the risk of sounding condescending, that had you done a little research prior to tearing open the device, you would have discovered that the iPhone 4 digitizer is bonded to the outer glass. This was much discussed, and often criticized both because of screen discoloration on new devices (until the "glue" set) and as being anti-DIY repair when the device was first released. Live and learn, I applaud your initiative in opening your device.