I reinstalled my Mugen 2 CPU cooler (the screws were loose indeed) and reaplied thermal paste. Booted my system and now CPU temperature is in 80-90°C idle I reseted my BIOS settings but the temperature stays at 70-80°C. What could have possibly caused this? I dont understand I'm worried my CPU is gonna get seriously damaged. Couldn't even go into bios without waiting a minute for the CPU to cool down.
Did you apply the Thermal Interface Material as recommended by the manufacturer? For example, Arctic Silver 5 should be applied to the CPU and the heatsink so it looks like haze.
-- Then add a drop the size of a rice grain to the center of the CPU.
-- Then you install your Mugen 2, and tighten until it is firmly seated, but not so tight as to warp the CPU heatsink.