White spot on cornea?

I took out my contact lenses last night and noticed a sizable white spot on my cornea and a little redness. I immediately thought I was developing a cornea ulcer, which is odd considering I never sleep in my contacts and I'm wearing a new pair. But this morning when I woke up, the redness was completely gone, and the white spot is practically gone. If I look closely I can see a tiny faded spot. It's obviously not an ulcer. I had one years ago and those things only get worse with time. What can cause this? And should I see a doctor? My eye looks normal again.