Is it real smooth, raised and round or oval? NOT serious at all. Mine went away on it's own. The only time you'd have to have it drained is if it got so big it would start causing you distress. My tonsil did get infected, after antibiotics the infection went away but the cyst didn't. When I went to the doctor for the infection I asked him if I had a mucus retention cyst there, he just said, "Yea, a little one". The cyst isn't an infection in an of itself. I noticed it in July, in October my tonsil got infected (infection cleared up quickly with Z Pack) and in December the cyst went away. If it's a mucus retention cyst that has nothing to do with strep throat. It's usually caused post nasal drip OR it can be caused by acid reflux.