I'm not sure why you used "force user" and "force group" both equal to nicolas. Do you have a group named nicolas?
Make sure you add your user to the host machine and then with smbpasswd to samba. If you don't care about sharing your printers with guest ok=yes, you could add that to your folder share too. If you want access to YOUR home files, uncomment the section where it allows that in [homes]
I presume you've studied the excellent documentation at
www.samba.org
Hope that helps; don't forget you have to restart samba after making any changes to smb.conf and that you should run testparm first.