My American pitbull terrier is 2 1/2 months old. I was playing with him about a 8 days ago and I all of the sudden noticed some lumps on his back. One very large (about 3.5-4 inches long and about .4 inches in diameter where it´s thickest). I also noticed a smaller one, about an inch away from the large one. This one is only about 1/4 the size of the larger lump. I can grab the lumps and squeeze gently and he doesn´t even seem to notice. I can tell they don't hurt him. I got him about a month ago and he is growing very fast. He likes to run under 2 twin beds that are in the room where I keep him... he bumps himself, pretty hard, right on the lower edge of the bed base, right on top of his spine where those lumps are. It is more often now since he has grown and no longer fits well under the bed. I've already taken him to the vet and he gave me a anti inflammatory treatment. we've gave it to him for 3 days and the seemed to get smaller, but now i think they are the same as before again. The Vet did a fine need aspirate and no puss came out just a bloodlike substance, but he could´t tell me what it was. He now gave me a treatment for an alergic reaction. I'm not very confident i should give it to him. what can these lumps be? They feel like a tendon or something but they don hurt him... he doesn´t even seem to feel them.