I had Restylane injected in mid October and I have this lump and horrible discoloration under my eye. What can I do?

Hello there! It appears that you either have a puddle of filler in that area, that the filler is causing fluid retention in that area, and/or it was injected too superficially. These problems can be remedied by reversing the filler in this area. I would recommend consulting with your injector about this. Good luck! Sarah RN BSN

I can appreciate how distressing this is for you. Because the skin under the eyes is very thin, the under eye area can look dark before you place filler to conceal the shadows, so I recognize that it is frustrated when you go through a procedure, only to have the same issue only potentially worse. 
The cause is the filler being place or moving such that it is too superficial. I would recommend having very small amounts of hyaluronidase [an enzyme that dissolves filler] injected into the area. If done carefully it may dissolve just the layer of filler that is too superficial, without removing all of it thus eliminating the need to be re-injected. This is my first approach when I am presented with this issue. Sometimes, I am able to get this resolved with minimal intervention.
I hope this helps!