Is a bakers cyst accompanied by fever & headache a serious health isuue?

After working out at the gym a few days ago i noticed a pain on the side of my knee. I thought I had probably pulled a muscle or streched a nerve..These last few days that pain has gotten worse and the side of my knee is now swollen and red. I was told by someone that it sounded like I had a cyst..I did some research and found that the type of cyst that I think I might have is a “Bakers Cyst” because the common symptoms match what I am going through. What I noticed is that along with the cyst I have been getting a pretty bad fever and headache at night that hasnt been letting me sleep..Could this be something serious? or is it normal to experience those symptoms…?