You can do an actual HDR with one exposure. While HDR should only be used with the right image and not all images, nothing ventured nothing gained when you learn.
Hopefully you shot in RAW.
1- Open the well exposed RAW, keep the good exposure. Tweak if you need. Save as a JPG
2- Open the same well exposed RAW file, but bring the exposure DOWN to -2.00 (or whatever works, trial and error at first). Tweak if you need. Save as a different JPG
3- Open the same well exposed RAW file, but bring the exposure UP to +2.00 (or whatever works, trial and error at first). Tweak if you need. Save as a different JPG.
With Photoshop, Photomatix or other HDR merge software, merge your three JPGs. Play with sliders.
There ya go... what I like to call.... ghetto HDR.
Again, images with a high range in the dynamic contrast will work well. Those that are bland might not work.