I had this problem about 1 day ago.
I found out that the problem was because my hd realtec audio software was stopped, so when i found and started it up the sound worked.
Maybe you made it stop or you made it not to startup when the pc starts up.
If that does not help try the ffollowing:
Play a music.
While playing the music put your headphones (audio jack) in an out and see if you get any sound.
Also goto sound settings and see if your headphones show up, if not something wrong with your driver.