Did you have a trabeculectomy?
Without looking at your eye, I can only postulate. It sounds like one of two things: the bleb itself is large and growing over the cornea or you have what is called epithelial ingrowth.
It is not uncommon for large blebs to droop over the cornea and even grow onto it. The treatment is scraping of the tissue off the cornea. Sometimes, you can inject some autologous blood to scar down and shrink the bleb.
With epithelial ingrowth, the cells grown down into the eye through an external connection (the wound from surgery). This can become a bit of a problem since they are inside the eye. They have to be completely scraped away or they may regrow. They can lead to corneal scarring or more ominously glaucoma.