What Causes A Lump At The Base Of Skull Along With Dizziness?

Hello, I recently got sick, started having a horrible cough, a little phlegm, body weakness and aches not bad though, as well as dizzy spells and my ears just started to feel congesited. When I pop my ears I get really dizzy to the point where it feels and seems like everything including myself were moving. I have recently found a bump on the lower part of my head right where the neck and head meet. Any reason why? It s on my right side, as well I noticed this once I started feeling sick my neck started hurting and then I discovered this.