If this bump has an order to it, this is a definite sign of infection. This could be an insect bite, possibly a spider. You should see a doctor right away to determine if it is venom in that bump. The doctor will use a syringe to test the venom and prescribe the right antibiotic for that bite. If the bump comes back every time you squeeze it or gets bigger everytime you release puss, that is a definite spider bite.