I got bit by something on my knee two days

Patient: I got bit by something on my knee two days ago. At first it was looking like a mosquito bite but it was really big and res around it. Now it’s just a bite Mark and it’s bruised all around it. But I’ve been feeling sick and extremely tired and sore ever since && it looks like a spider bite but the two tiny bite marks are so small I can barely tell.. It’s really bruised now though and hurts to touch. Any idea what this could be?

Doctor: