If you notice there is some brew bubbling around the Carbonation Dial don't worry! This is a good sign that the brew is fermenting away nicely.
This is simply the Carbonation Dial self-regulating the pressure and allowing some of the brew to come out along with the CO2. This is most likely due to the Pinter being ever so slightly overfilled.
This is normal and doesn't indicate any fault of any kind. All you need to do is wipe this away as it appears and not let it dry as this will be harder to clean.