My 10 year old gsd is limping on his leg with a plate in it?

He got his front right leg stuck between two logs one day in the woods when we were walking when he was around 5-6 years old and it broke, he got major surgery and now has a plate in it, the plate has been in since that time, he hasn't had a problem with it in probably 2-3 years. Yesterday he started limping and being very lame on it, he will still put it to the ground but you can see the obvious shoulder drop and limp on it as well. He is being very lazy, panting heavily at times, licking his leg, and can't/won't go up the stairs. He is staying in the basement and the garage and won't go outside either, one of his favorite things... he is allowed to run freely. I am only 15, I can't take him to the vet myself, I don't know what to do. I have been asking my parents to take him to the vet but they seem to think that he just hit it off something and it is sore. Me, I don't think so... Should I MAKE them take him to the vet? Or should I wait it out with them to see if it is only sore? Thanks.