I accidentally disconnected my internal hard drive

Well, you cannot "disconnect" an internal hard drive unless you physically remove it. So perhaps you could tell us exactly what you mean.

So you've been running your computer without an internal hard drive for months? How?

And how did you accidentally disconnect the drive in the process of trying to rename it? Renaming a drive is a click-once-and-type-the-new-name procedure, not a job involving screwdrivers and opening the computer's case.

There is no triangle on the Desktop icon for your drive. If this is something you did in iTunes, then you need to tell us what you did. We have no other way of knowing.

When an iPod is connected to iTunes there is a gadget that appears to the right of listing in the sidebar. The triangle is pointing up. Click on it will Eject the iPod so you can unplug it from the USB port.

Your hard drive is internal. No USB port, no Eject triangular gadget. In iTunes there isn't even a listing for the hard drive.

So, please, provide us a detailed and exact description of your issue because so far nothing you've reported makes sense.

I looked up "triange" in the dictionary and the word could not be found. So you need to help us out here with what you are describing.

The word he meant is "triangle."

Then you connected an external hard drive, a flash drive, an SD card? Now what? Clicking on the triangle enables you to unmount that drive.

Rod the internal HD won't have a triangle next to it. It sounds like you may have unmounted an external HD when you clicked on the triangle however remounting it is as simple as unplugging it from the computer and plugging it back in.

I don't think you did any harm whatsoever.

Roger

Open Finder preferences, select the Sidebar icon, check the box for the desired items you want displayed. If all is well then what you did was to Eject an external drive, not your main hard drive. You can verify that by looking on your Desktop. If you see Macintosh HD or the icon for it then you're OK.