distribution of uneven screen brightness.

I was working on my laptop and the screen light was alright. But suddenly the lower left part of my screen brightness got dimmed though the other part of the screen is alright. What should I do now???

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0