>>> sorry dont know where else to post!'
'Technology' would have seemed the obvious place to me but it doesn't matter as long as people still see your question.
The first thing to do is to click on the loudspeaker icon at the bottom right of your screen. If there's a 'No Entry' symbol showing there, clicking on it should restore your sound. If that symbol doesn't appear there, click on the loudspeaker symbol within the vertical bar that's appeared to mute the sound. Then click again to (hopefully) restore it.
If that doesn't work, try rebooting your computer. (It's amazing how often "Turn it off and turn it on again" works!)
If you've still got no sound, try another set of headphones. (Borrow some or fork out a pound or two for a cheap set of earphones in a discount shop). Assuming that they don't work either, the next step is to reinstall the sound driver on your computer. That's a fairly easy task but, to make it easier to provide you with instructions, it would help to know which version of Windows you're using.