Check CPU Temperature Using Sysctl in Terminal

This model of MacBook Pro has a totally passive heat sink, so the two temperatures you mention are on the main die / logic board and not some measure of how hot your heat sink itself is running. The only way to correct this difference would be to have a new logic board installed (or get a new CPU mounted on your logic board).

As a technician, I'm more worried when the heat sink isn't closer to ambient than to the core when stressing the CPU with constant computing load. Then, it might be worth it to crack the case and re-apply the thermal paste between the metal cover (the CPU heatsink) on the logic board and the finned device (a.k.a. the Mac heat sink part) that gets the heat from the CPU heatsink to the air flowing out the back hinge area of your Mac.

If you had a faulty CPU you should be able to expose that in a geek bench test where it would throttle itself down under premature overheating. If you still had warranty left, I would open a support ticket (visit a genius bar or call AppleCare) to document this. They can then enter your concerns and offer a logic board swap if you are out of spec. I've had good luck getting concerns on the record and having Apple cover a repair if they had the chance to cover it under warranty, chose not to, and then the device failed within a few months after warranty.

Lets me try to help you to understand what is going on here:

Any third party software uses the already available information from your Mac as designed by Apple that uses thermal diodes attached to different points in the system. Apple has done a lots of work to correctly manage the thermal load already.

The coding and the mathematics to covert the given information correctly in to the Temperature readings outputs by third party software could be tricky, so use it with grain of slat, since it varies a lot from Hardware (diode) + EFI + CPU types from system to system. In English, the third party software's are not always calibrated for your specific system.

Note from Intel:

Intel® Processors have built-in thermal protection. If the processor gets too hot, the built-in protection shuts down the computer. If your computer is not over-clocked and is running under the design specifications, the built-protection can help prevent damage to your system.

High Temperature readings:

If you use a third party software to measure the temperature or the Extensible Firmware Interface (EFI) readings, contact the software vendor to ensure the software is validated to work with your processor.

If you still want to know more or you see weird Temperature reading, please go to Intel web site and look for your specific CPU specifications. It can not be hotter outside then inside since the CPU is the source of heat, otherwise your computer will just shut down initiated by Intel's CPU internal protection.

However, if that happens (the shutdown by the CPU), then you need to repair your cooling system (fans + heatsinks ect.)

So I just looked up at Intel for my Intel Core i5 (1.8 Ghz) and it shows Maximum temp to be 105 Degree Celsius and it has the build in thermal protection.