pydah santosh, the very first thing you want to do is to '''not''' try to restart the phone. This may further damage your phone. The next thing to do is to clean it. Disassemble your phone using then clean it with +90% isopropyl alcohol. Follow [guide|5825|this guide], and even so it was written for a 3G all the points are still pertinent to your phone. When it is properly cleaned, ''' replace the battery'''. All these steps are to avoid delayed failure caused by corrosion. Once all this is done, reassemble your phone and reevaluate. It is possible that it is "only" your digitizer that may have failed, but it is also possible that you are having touchscreen IC problems. While you clean your board, check for any obvious damage, like burned or missing components etc. If there is no change you could start by replacing the front assembly. Hope this helps, good luck.