I developed a white patch on my gums three days ago. no swelling or pain, and it doesn't seem to be spreading.

Keep a watch onit: White patches in the mouth can be due to more than one cause, mostly these are benign and may go away with time. One called Leucoplakia can persist for years and may require monitoring by an oral surgeon or a Dentist. Show it to your doctor next time you see him/her. It is not likely to cause any problems over the coming few months or may be even years.

White spot: There are a number of things that can cause a white spot. It can be caused by trauma, irritation from foods, chemicals, infection, and several more. Most spots will heal in about a week. If it does not heal you should see a dentist and get the spot checked.

Could be: Could be quite innocuous or quite serious. If it fades and disappears in another week, just report it to your Dentist at your next regular check-up. If it does not fade and disappear in a week (10 days from onset), call your Dentist immediately.