He was rubbing his nose on the glass. And did notice him rubbing his nose on rocks earlier as well as a single spec on his top fin. I assumed it was ick so I dosed some copper. His nose appears worst as you can see in the picture.
Puffers can be sensitive to copper, depending on which type you're using - cupramine or coppersafe should be ok if you're careful not to overdose. Do you have a copper tester?