Locks on files appear when you are using a client application to edit the file. This is normal and expected.
This is not the same as a check-out. You can find more information about this on the following link:
http://www.novolocus.com/2012/07/25/sharepoint-check-out-vs-lock/
Sometimes the lock goes away after around 10 mn after you close the client application.
If this was not the case, then you could use this tool to release this lock:
http://think4code.blogspot.pt/2012/07/sharepoint-2010-file-is-locked-for.html
Download tool: https://spunlockfiles.codeplex.com/
