maybe it was the curing time? My new fx 6300 build is also at about 50 C. That's more likely with pre applied thermal paste. And room temperature is maybe also a factor, I wouldn't worry about it.
Room temperatures are important in factoring your CPU temp. Where I live, it's starting to get warm (FINALLY) and I've noticed my temps have also increased. In the winter, my CPU was hovering around 35C, now it's around 42C (It's strange, I gotta look into air flow after finals) on my Hyper 212 EVO. But the important thing to note is that your CPU/GPU temps will fluctuate as ambient temps fluctuate.
need way more information on OP build. I had to de-lid my Intel and apply new paste, which was a bit frightening but more information would help find a solution.
id say need specs .. but also cpus ramp up during power up , so it lowers when windows boots which is normal but id say get some prem thermal paste and apply it.
but cant say if temps are ok unless we see some specs