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If you are not inclined to see your vet just yet, there are some things you can do at home. The first is to slow him down. Basically put him on bedrest. He can lay at your feet or in his kennel for the next week. But no walking, runnning stairs or playing. Only take him on a short leash walk to use the restroom and them back into his confinement. Even if he starts to walk better, keep doing the restriction for the full week.
Do not give him tylenol, aleve or aspirin. They can all have serious complications. And if he is really in pain, he won't respond to conservative treatment, your vet can give you better medicatiosn for dogs. But if you start him on your household drugs he can't get the dog pain medications later.
If you can feel a tight muscle or he seems painful when you pet an area on his leg, you can warm pack his leg. Use warm water on a cloth or microwave a damp cloth. Place the cloth in a ziplock and test it on yourself to make sure its not too hot. You can warm pack 2-7 times a day for 10-15 mintues each time.
If the leg does not get better after a week or gets worse, you know its time to see a veterinarian.
I hope this helps