A few days ago, we've taken this little pup in after we found it outside on a cold winter night. I remember how it didn't warm up to us at first but gradually became more cheerful, albeit shy. It liked jumping onto my thighs whenever I kneel down. Eventually we found its owner. However, it turned out to be the wrong dog, so I was thrilled to keep it for a while longer until we find its actual family. However, now, whenever I try touching it, it always bites (or attempts to) my hands. I let it happen sometimes because it's just growing teeth so it won't hurt me and someone told me that it'll gradually get closer to me. But it hasn't been working at all, because whenever I'm near it always bites me. I'm noticing that it has bloodshot eyes too. Sometimes the biting even gets really hard and I pull back because of the pain of the teeth chomping down harder. Plus, when it tries reaching for my hand to bite it goes on its two hind legs and digs its nails onto my leg which very hurts. But the thing that creeps me out the most is its bloodshot eyes, as if it wasn't living in a town full of humans but in a forest.
This is my first time owning a dog--a pet for that matter-- Tomorrow or the day after, my family member will take the pup to the vet. Honestly, the only thing that makes the pup calm down is about thirty minutes of calming music for puppies I found on Youtube.
Sometimes, I wonder if this was really the same dog that was shivering on that nights days ago. I feel like it's just a pup and it doesn't know that biting people aggressively is bad, or I'm just that tasty, but I'm no dog expert. Any answers to why it suddenly had a personality change?