blood filled lesion on dogs back

Question
I recently noticed a spot on my dogs back.  looked like a small hole. like maybe a bite from another dog.  my dog is confined to my back yard and can not get out.  i cleaned he area and put some neosporin on it....  over time it would drain,  so i would squeeze it here and there to get out the puss.  it was a pink fluid and every now and then i would see these little white small things  come out with the puss.  they looked like very small white (lines) not long at all. they were not moving and did not appeared to be  alive.  I don't know if it was his bodies way of removing foreign junk..  can anyone tell me anything.  also it has gotten better.  the area seems to go down when expressed...  a few days later it is filled again and now with what appears to be just dark blood.  once expressed it flattens and then we start over.

Answer
This sounds like a cyst to me as they go through the exact stages you describe if they are expressed once they are "ripe". I haven't a clue, though, what the "white lines" would be unless flies are laying eggs in there. UGH!

After you treat the area, try to cover it so that the bugs can't get in there. I know this can be hard to do, so I would bring him into the house until this heals up.