For immediate treatment, you can give one (1) adult 325 mg aspirin. Use aspirin, not Tylenol, Aleve, Motrin or other human OTC pain medication. You can repeat this twice a day, but you may not need to if he seems sounder by tomorrow. The most common side effect is vomiting, which often occurs at doses near the therapeutic level.
Keep your Golden boy as quiet as possible. Cold packing will help reduce swelling. A cold wet towel works well. If you know it is his paw, treat the paw. If you are not sure of the exact location, pack at least above the carpus (joint above the foot). You should be able to localize the pain by flexing the joints of the foot, carpus, elbow and shoulder, and by palpating the bones between the joints.
Try to keep him quiet for at least a couple days. I know this is hard with a young Golden. If he is crate trained let him rest in the crate most of the time.
A vet visit early next week would be indicated if the lameness continues or gets worse. This would rule out fractures of the smaller bones of the carpus and foot. Pain control drugs available through vets are more effective and safer than human OTCs.
Let me know if you have follow up questions.