how to handlehandle thumbnails file.

[AC Question]

I have karbonn titanium s1 plus and it's internal storage is 1 gb. I have free space about 700 mb and then a thumbnail file create and my internal storage is full. Now when i delete this file through ES file explorer the file deleted but the space not release. And when i reboot my phone a file creates in Lost.dir of the same size as thumbnail file. give me better suggestion to handle it. I don't want to reboot my phone 100 times in a day