I Have A Bump Behind My Right Ear. I Had

I have a bump behind my right ear. I had a sinus infection and am currently taking medicine. I have headaches too and when I went to a walk in clinic a while ago I tested negative for strep, but she said my throat was red and had drainage in the back, and that possibly my tonsils looked swollen. She said she could not treat it cause there was nothing to treat, plus I had no strep throat. I don't know what's causing this and if we're do to an injury all I know is that my baby threw one of his toys, which accidentally hit that side of my head but I don't know if that's what is causing the bump.