What Causes Red Bumps On Face?

I have had several occurences of red hard bumps on my face - 3 or 4 occurences on my chin and once on the tip of my nose. They are very sore to the touch and the ones on my chin eventually had a white head appear. The one on my nose was just very sore. I have not eaten anything different nor have I used anything different on my face. What could they be from? I am retired and living in Florida with absolutely no stress. Any helpful ideas?