A dog came wondering into my home..Please HELP.?

Ok. So me and my mum and her friend were watching some T.V. and a dog came walking into our house. It was choking so we went up to it and it turns out his collar was WAAAY TO TIGHT. The person that put it on made an extra hole which was far far down from the other real holes. Once we took it off the dog took a deep breathe and then licked my mums friend. (Who took it off) Now this was yesterday. We tried to make the dog go back outside but it just walked around and circles and wandered out onto the road and sat there. He nearly got hit! He isn't fixed and he doesn't have shiny fur, it looks kinda weird. The dog is a black lab. I would say he is about a year. Last night my mum fed him cassarol. Because we don't have dog food. I don't know what to feed him right now. O.o We have no more cassarol or anything really. What can I feed him?? Also he keeps biting at his tail area. I dunno why. It's like he's trying to chew all his fur off. He's cute and very nice though. With huge dark brown eyes. My mom is going to put him in the paper and on the raido. I don't want him to go though. But anyway. What would you do? What can I feed him?