leg pain and blisters

Question

  Our 10 week old female blue heeler came from around the house two days ago limping.  Her left leg seemed to hurt so bad when we bent it and pulled it down.  Yet, when we poke, prod and rub, she doesn't seem to care.  
 Yesterday there were about four blister like sores with odd shapes under that left leg where her tummy and thigh connect.  She didn't feel like eating, and wasen't her usual hyper self.  Today they are gone but one large one.  I put A&D ointment on the sore(s) and have been giving her 1/2 a St. John's asprin every few hours.  She cannot walk on her left leg, therefore, she hops along when she goes to eat or potty outside.  She has all of the symptoms of hip dysplasia, but why is there a large blister under that same leg?  I don't see how ants did this and I have surfed the web all I can and nothing seems to fit her discription. Our four and a half year old heeler has never had health problems, so I am perplexed.  Help!

Answer
The best advice I can give you on this occasion is to take the pup to a vet.  An injury like that with pain on manipulation requires attention just in case there is a more serious problem.  Delaying veterinary treatment may exacerbate any damage that has already been done.  As far as the blisters are concerned she could have been bitten by something and be having an allergic reaction to it.  At this point I would say they are a minor consideration compared to the joint pain.
Also please dont give such a young pup aspirin without taking advice from a vet, aspirin can have some side effects in dogs including kidney and liver toxicity and is not really a recommended remedy for dogs in most situations.
hope this helps
Sarah