Whats happening to my Cyst?

I have had a Cyst on my upper eyelid for a good half a year now. It has been fine up untill recently, it has doubled in size so i have booked an opointment with my local hopsital; which isnt untill a white. My Cyst has suddenly drooped over my eyelashes and has a yellow tip, which is slowly getting bigger is this just my Cyst going, or is it something to worry about?