Pressure on the perineum can be relieved by

1. Different saddle width and shape
2. Bike fit
3. Saddle angle
4. Shifting around and standing periodically when riding
5. How upright you ride. Sit up and begging type position is typically worse.

I'd get this fixed before the big boy loses his edge. Sounds like it is a combination of the above. FWI....I am trying the Specialized Romin in the 155mm width and might try the Selle Anatomica.

If you don't mean the perineum, are you talking about the inner thigh? If so, the saddle shape and wide wrong or the saddle is too far forward. See a good bike shop.