Sure, and thanks for responding.
So it actually seems the problem is related with putting the computer to sleep. Now, when I close the lid of my computer (without manually pressing the sleep button as before), the screen remains lighted with a black background and the cursor is visible.
After a minute (or two), the screen eventually turns fully black like it's supposed to.
I turned off my laptop, turned it back on, and tried to replicate the problem for a picture, but it went immediately to sleep. This probably means that after "continued use" (don't know the proper term but I'm sure you guys know what I mean), it exacerbates.
Would a PRAM reset work? I believe there's also another reset I can use but don't remember what it's called.
Seems that another person posted same problem on Apple Discussions:
https://discussions.apple.com/thread/5273980?start=0&tstart=0
Edit: Did PRAM reset. Will update if it works out. However, this seems like a problem that a lot of people have had and Apple has not addressed. Similar variants have occurred since 2009 I believe so not much to do at this point unless someone here knows something.