I HAVE A STUD RING UNDER MY LOWER LIP, ABOUT 1/2 INCH UNDER MY LIP, AND ITS BEEN IN FOR A YEAR.  JUST IN THE PAST TWO MONTHS iTS BEEN SMELLING WHEN I SMILE-IT COMES OUT A LITTLE, AND HAS AN FOUL SMELL.  I HAVE TAKEN IT OUT AND WASHED IT BUT AFTER A LITTLE WHILE IT SMELLS AGAIN.  CURIOUS IF THIS IS AN ISSUE WITH OTHER OR NOT.  I KNOW THAT EARING GET A SMELL FROM TIME TO TIME BUT I CANT SMELL THAT, THIS IS RIGHT IN FRONT OF MY NOSE.
Hello there, There is a chance that your stud ring may have got infected. This in turn leads to a pocket of pus forming under the ring and whenever it is squeezed which in your case it is when you smile the pus oozes out of your skin where it has been pierced. It would be advisable to consult a general surgeon who can Chat Doctor.  Also, you may have to get rid of the ring and this will help the healing. Hope this helps,