Tonsil Cancer Symptoms?

Hi, about 5 weeks ago I had a sore throat on the left side. Upon checking I had a a few small white spots on my tonsil. 
 

I developed a head cold and it came and went. I feel like I have a slight post nasal drip with a need to 'clear phlegm' over the day but not spit it up. 
 

I went to the doctors as the white spots were still there and she put me on a dose of antibiotics and nilstat. These didn't make a difference. My tonsil is slightly enlarged now, gives a slight burning feeling and like I have something stuck there at times. 
 

I wonder if this is a sign / symptom of tonsil or oral cancer? Or could it just be tonsil stones that are perhaps infected now?