Suggest Treatment For Dots On Skin After Insect Bite

my husband got bit by something and I am trying to decide if he should see a doctor or not. it happened 3 days ago day one it looked like a normal bug bite day 2 there was a knot around the bite, it became hot to the touch and spread to the size of a quarter and right where the bite happened there is a dot with a circle of dots going around it day 3 (today) it has not changed to much it has just spread a little more