Can Someone Tell Me What This Is

As you all know I have been sick for the last week, so when I got a fever blister (cold sore) I wasn't shocked. However, now I'm not thinking it's a fever blister.

Can someone tell me what this is? I am no

w starting to think it's a spider bite, due to the red circle around it. At first the red circle wasn't there but now it's getting bigger.

Should I go to the doctor? I have been putting tea tree oil on it and the blisters seem to be getting better but the circle is getting darker and bigger.

What should I do? What do you think it is?