[Troubleshooting] CPU running way to hot

I must have auto-overclocked my i5-2500k and now it's at 4.8 Ghz, which is going to be too hot for my fan. How can I downclock my CPU? Or maybe restore it to default? I heard that I should remove something called the "cmos" for one or two minutes and then put it back in to restore it to default. If it helps my motherboard is an ASRock Extreme 3 Gen 3.

My CPU is running about 60-65 in the eufi thingy.

Any help much appreciated!