How to tell if a blister in your foot is infected?

How to tell if a blister on your foot is infected? Okay. So I went skating last night and got a horrid blister on my foot. Now I'm worried its infected. The actual cut is about as wide as a pencil eraser, but the redness around it has the circumference of a quarter. It doesn't really hurt, nor does it... show more How to tell if a blister on your foot is infected?

Okay. So I went skating last night and got a horrid blister on my foot. Now I'm worried its infected. The actual cut is about as wide as a pencil eraser, but the redness around it has the circumference of a quarter. It doesn't really hurt, nor does it smell bad. But I'm still worried. Ten points?