only one side speaker working on laptop
 

how to check if the other one is blown up or, some settings are to be modifired?

Start the computer using a liveCD/USB. Do you have sound?

i already tried,
Still only one speaker is audible

Well, considering all facts, I'd conclude the speaker is failing.

Hook up some external usb powered speakers to the headphone jack.

For external speakers, the simplest test to to try them on another computer or device which can accept them. If you have two sets of external speakers or a set of headphones, you can also test with them and compare results.

i realised reading your response that i had put the word external in thread accidentally.
i meant internal laptop stereo speakers only.

In that case, if the problem persists when you boot to a live CD of something else and if external speakers/headphones work properly, it is almost certainly a hardware problem or a small set of external speakers. (We all have brain skips from time to time; it's not like I haven't had one for almost, say, 15 or 20 minutes.:))