HOLY FUCK!!!! did they give you like options what this could be? i mean they should have at least some idea what causes similar damage. I bet that hurt like a mofo, glad it turned ok "ok"
EDIT:
well a quick google search yielded this
possible culprit :Brown Recluse Spider
http://www.emedicinehealth.com/spide...3_em.htm#Brown Recluse Bite Symptoms