Recently I Had A Boil Under My Arm (pit). Walk-in Clinic Doc Put Me On Antibiotics And It Pretty Much Went Away But Now There's A Cord Or String Like Thing There In My Armpit. What Could It Be?

Update: Hey thanks everyone for your input! Well I ended up going to the doc and she said she "thought" it was thrombosis of a vein and that "maybe" the boil had somehow pushed against the vein causing the blood to clot.  That makes sense to me as the cause of the "string thing"... She gave me another round of antibiotics and in a week or so it was just about gone. Completely gone after about 2 weeks. It's been about a year or so now and all is well. It has not come back and neither has the boil. I did end up with a little fascination with boils and started searching the net for anything I could find. Anyone with a boil should checkout youtube and search for boils. There are some pretty crazy videos of people having theirs popped. WOW...

Sounds like you need to see you PCP. Although you were given an antibiotic, most boils are usually lanced to let the infection drain out. Boils are also contagious and you made get it again in the same area or some other area.

Maybe the boil and the cord are unconnected - it is possible they are two separate and unrelated things, which just coincidentally happened in the same place on your body.  Boils in the armpit often come from having pulled a hair out of there, and are quite common.  
As regards the cord thing, I have the same thing, just as you describe, but doctors can't diagnose it, despite doing ultrasound.  They say it is not a vein or a nerve, but most likely a band of tissue that has come from out of the muscle.... But they say there should be no such band in the muscle, so they remain mystified.  Good news is they are sure it is not a sclerotic vein or thrombosis.  You should see a doctor though.

Has the boil not perhaps popped? Sounds scary, I'd be freaking out. Can you pull it out? Is it a natural substance?