Why are my dogs paws bleeding?

I have a 1 year old male cane corso mastiff. He's mostly an indoor dog, as he and his sister run away if we let them out unsupervised. Recently I've been noticing blood spots on the floor inside and wasn't sure where it was coming from. Then i started watching Romeo and noticed it was coming from the bottom of his paw. I think it's only his 1 paw, but he seems to be in a little pain from it. i attempted to wrap it in a wet rag for a few seconds, but he pulled away. I heard something about bugs in dogs paws, but am not sure if that's what it is. Please help my puppy!