Anyone have this problem?

So my dog has been limping he won’t walk on his right front leg. He won’t play with the dogs or play around the yard like he usually does. Absolutely no idea what he would of done to it. I tried touching it and moving it around and he had no reaction? I’d think he’d Yelp or something if something was really wrong. It’s not swollen. This is going on like day 3 now that he’s limping. And he’s only 4 years old. I do plan on calling the vet. Just wanted some opinions since it didn’t seem to bother him when I was messing with it?