What Causes A Swollen Lump On The Tonsil?

i have had a lump on my tonsil for 4 weeks. it looks like one of the smaller glands on my tonsil has swollen to the size of a small grape and changed colour (the skin has changed colour no puss) i went to m doctor 4 weeks ago and had a big course of anti biotics, this did nothing, i went back and had a blood test for infections this came back clear. i was told it would just go away on its own. but this lump is solid if you touch it and i am a little worried about what i should do next