Diagnosis: neglect. I don't know that it needs to be quantified/qualified to any more decimal places than that. The placement above the heat register is problematic if the register is operational. Even if it isn't operational the sill of the window is rather high and IMO the plant could benefit from being raised several inches. Actually, it seems to me that if it was able to survive the winter outdoors in your area it is at least past the worst and at least outdoors it would be getting a ton more light and lots more air exchange all things that would help, not hinder its recovery. The bump is the larval form of an alien lifeform (extraterrestrial). Being plant based it is probably slow moving (probably) and will wind up being a cat toy if and when it hatches out from the polyp.

H

Okay... well what I can do in my apartment room is open the window so I'll do that. I put it on the heater just to take the picture, it's on my desk a few inches up and gets plenty of indirect light.
But is the spreading yellow thing fungus?
I'm a little scared about the alien, I hope it doesn't get much bigger.

No, the spreading yellow isn't fungus, it's just the leaf dying. The black spots probably were caused by fungus, bacteria or exposure. You probably can't do much to help the leaf at this point (it doesn't seem to be actively infected) other than to give the plant more light so it can better build up its immune system. Since this is a cattleya, it needs more than indirect sunlight. It should probably be getting at least a few hours of direct morning/evening sun per day to be happy.
~Jem

Thanks Jem, that's exactly what I needed to know! I can definitely give it several hours of direct sunlight, and I'm glad it's just going to lose a leaf. Phew.

I would repot that plant and get it in the sun.

Jane