The data is stored in file status.dat. Find this block of code in your nagios.cfg
This is the setting for **status.dat **file location. I'm not sure you could view it with regular account, but that is relative to your linux installation. Take the SU account for viewing it, but be careful not to change the file in the wrong way, I suggest you make a backup first before doing anything with the file.
Also there is retention file if you have retention options enabled (it is used for remembering host/service states when Nagios is stopped). There is also a setting for it in the nagios.cfg:
State Retention File