Not rooted phone white triangle and yellow exclamation point

[85snowbutcher]

Hi My phone is not rooted, in face I have no idea what it is. I have a task-switcher application which I often used home button multiple times and this time the phone just stopped working, I could not turn it off or do anything else so I pulled off the battery, Once It was done the white triangle with yellow exclamation point showed up. I tried to reset, reboot, update but nothing is working, what can I do? Please help