How to update my android OS? Before two months my mobile phone was up to date in Android OS. I have updated my phone Nexus 5 to Android Lollipop.

And After on Month, My mobile phone display was damaged,And i sent it to the LG service committee, because it's on guarantee.

After the mobile service process completed, at once i have made an update process. But it was not installed the latest version of Android(Android 5). Up Till now i do check for update, I display nothing for my query. How to fix this problem?

Do you have any idea about what the service team has done to my phone?
Try a hard reset and then update your phone by going to Settings &gt; About Phone &gt; Software Update

If you would want to do a manual update then you flash your device and then install Lollipop image. For more instructions see this link