Bubble-eye is a disease, so if it looks like skin forming the "bubble" then it is gas bubble disease, which I am not very clear about, but has to do with oversaturation of gasses in the water, solved by air stones, splashing filter return, etc.
Hopefully it was just a sticky air bubble and is a thing of the past. One of my peacocks had a large white ich-like spore on his lip and I started to get my quarrantine tank set up, until he bumped the glass and it fell off - it was a grain of sand from the substrate.