I was just bite/stung by something on my walk home from work. I was wearing tight pants and felt a sharp pain on the back of my calf . I thought it was just my pants catching on a hair or something, so I moved my pants but it still hurt quite a bit. I looked down and didn t see anything. It hurt just to walk - the pain was radiating in a large area. I came home and took my pants off to find a bite/sting about the size of a nickel (not abnormal for me - my mosquito bites usually get that large). But it s been about a half and hour and now the area has grown to larger than a silver dollar. The skin is sensitive all around the bite, further out than is red. I can see some of the veins around the bite are swollen slightly. There is a clear red dot in the center and while it s mostly circular, it is not a perfect circle. My calf muscles have been twitching repeatedly. I do not feel short of breath or light headed. What the heck happened and do I need to be heading to the doctor/hospital?