Inodes in linux

every file condain one indoe which encloded metadata of file or folders like owner id, user id, group id, modified dates, size, timestamb. ..

#df -i

#ls -i

#find . -inum 213456
//here your inode file will display

#find . -inum 213456 -delete
//here your file will delete along with inode, don't do this without any confirmation.

if you have any "file permission exist error" please check inodes, if it's been full you will get this error.
you should remove unused inodes then you get rid out this issue.