Given that the actual audio levels depend on the final output equipment and the distance/coupling between it and the sensor or ears there is no way for your computer to monitor the actual audio levels without a calibrated sensor or microphone placed where your ears would be. In the case of headphones and especially in ear headphones this is especially impractical.
You can purchase such sensors, some with a connection to the computer, but headphones do make these a problem.
Note that the readings in dB are a log scale of the output levels not the actual audio levels which are measured in dB(A).
A good rule of thumb is that if it is loud enough that you are worried it is probably too loud!
It is also important to note that the type of sound and the duration of exposure also have a significant impact on hearing damage as well as actual sound levels.