no problem, a year ago, I would have thought the same thing about that weird dust under the heatsink lol.
I have the same processor as you, the most hottest ive ever let it get was 61c and that was scary as hell. as of now, I absolutely won't let it go over 52c. when gaming it usually hangs around 45c clocked at 4.0ghz.
+1 for all of the grain of rice application suggestions here, its never failed me. put the paste right in the middle and squish down the heatsink. latching the heatsink down will do the rest of the work for you

also aftermarket cooling would be a good idea if you plan to overclock. I like the corsair H series all in one water cooling systems(I'm using the corsair H50), however, for a cheaper option the cooler master hyper 212 will be more than enough for that processor and some decent overclocking