My dog has an injured leg or pae or something.?

I have a very healthly beautiful 2 year old Italian Mastiff. He was fine last night when we went to sleep. He sleeps on the floor next to my side of the bed. When He got up this morning he couldn't walk. He is favoring his front right leg or paw. The poor thing wants to do his usual following me but he only made it to the living room and plopped in his bed out their. I can't even get him to come to me so I can take him ouside. And I am not about to attempt to carry him out to use the bathroom. it's 6:30am so I have a little while till my vet is open. Hust seeing what people have to say about it. Maybe something will ease my mind