My dog has a callus/dry spot what can i do for it?

He's about 7 years old and sleeps on the floor which is tile and sometimes sleeps outside. He's a german sheperd mix . It's swollen and hard. Any suggestions on what i should do for him? And will it ever go away? An is there a probabilty that he will get it on his other elbows? Should i take him to the vet?