What is this bubble under my eye years after Restylane in tear trough? (Photo)

I had restylane injected to fill out hollow under eye area in 2009. Most of the filler has dissolved but there is one area under my right eye that looks like a bubble. When I don't have makeup on, it looks blue like a bruise, but it's not going away. I have massaged it, put cold and warm compresses on it, but it's not budging. What could this bubble possibly be?




