[Plugin: Yet Another Related Posts Plugin] Help WP Error : open(/home/ptcbuddi/tmp/

After installing Plugin: Yet Another Related Posts Plugin, i got error at the botton of WP-Admin and pages :

Warning: Unknown: open(/home/ptcbuddi/tmp/sess_1846c18e27eb1b66a57ece88f0c7ed6b, O_RDWR) failed: Permission denied (13) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct () in Unknown on line 0

Please somebody help me to solve this problem. Thank you

Regards,
Rudi