(1) As stated, most likely cause is improper HSF mounting. Need to verify that ALL four white nubs are protruding equally on the back side of the MB. (Might want to google "how to install Intel HSF). Remember if you remove the HSF you will need to replace the Paste. Most use artic silver 5.
(2) Bear in mind, that while this may bring your CPU temps down (should be below 65 C based on a room temp 72F, and 50-> 75% CPU utilization, The stock HSF is one of the poorest performing HSF.
(3) Myself, I do NOT even take out of the Box - it is best used to keep the box from blowing away. The most often recommended 3rd party HSF (performance vs cost) is the Hyper 212 - About $30. Remember the cooler the better.