I Have A 3yr Old Beagle-Jack Russell Mix. He Has

I have a 3yr old Beagle-Jack Russell Mix. He has always been very healthy, with no problems. The other day he was running around the kitchen island (slate floor) and let out a big yelp, and at the same time held up his back left leg. Within 30 seconds, he had his leg back down and was running around, up steps, etc. with no issues. The next day he was excited that we come home and was running and jumping on us, and yelped again holding that same leg up. Again within 30sec-1min, was running around no problems. Then last night he was walking around in Kitchen and yelped, this time holding his ears down while holding that leg up. The recovery time was a little longer - about 2 minutes, then back to normal. He almost refuses to let anyone near his nails, so they are a little long, but I didn't think that could cause any major issues. Can you give your opinion on what could be causing this issue??