and try smc reset as well
I would also do the PRAM again
Look in the headphone jack and see if there is a red light on, if there is try plugging and unplugging a set of headphones in and out a few times. You can also go to utilities>audio/MIDI set up click the output tab and make sure it is set to internal speakers. Sometimes just putting it to sleep for a few minutes using the sleep command from the apple menu and waking it will restore normal function. If the red light persists, you can try a Q tip with the end cut off and GENTLY try massaging the headphone jack, there is a micro switch that sometimes gets hung up. Stop at the slightest resistance. All the best
I tried everything; the smc reset(with and without headphones plugged in), putting to sleep and waking it up(Several times), resetting(several times). I also tried to set the "Internal Speakers" as the output source from System Preferences>Sound>Output and also from MIDI but there is no "Internal Speakers" option in neither one of those, there is only "Digital Out". The red light was on in the morning and it was off since I got home(2 hours), but now its on again...
Thanks, Pennbank, for the great help by the way, the information on those links is pretty wide. Let me know if there is anything else to do please.
Ok, Problem Solved.
Since I didn't have much else to do, I went to the Apple Store to ask whether its a hardware issue or not and I discoevered that the Apple Stores in my country are ripping off the people who are in need of assistance with their product. They told me that something must've been stuck in that little hole where you connect your headphone and it is really hard to interfere in that area since its so sensitive... The funny thing is that they told me since they might not be able to interfere in that area they will more likely replace the "main operating card" or something(as I don't know the equivalent of that word in English) with a new one, and the price for replacing that card starts from $500.
This morning I still didn't have any sound and the problem persisted until now. I woke up the computer and bam!, I got my sound again. I think its a temporary problem, you just need to wait until it just fixes itself.
Thanks for the great help though, it helped me a lot.