iCloud Problem HELP PLEASE!!!.

i have a problem with iCloud, as i click the home button to after ''slide to unlock'', i can't '' there is a constent message saying ''Not Enough iCloud Storage'' '' Some of your documents or data can't be saved to iCloud.You can manage your iCloud storage in Setting. underneeth the message it says ''Close'' Or ''Settings'' i can click on both buttons and it won't go away i can receve calls , i can't awnser them i can't do enything while the message is there i can only Lock the screen and press the home button to put it back on thats it PLEASE HELP..!!!!!!!!!!!!!!!!!!