Limping and I can't find a reason why

Hi. My 4 year old Yorkie went outside to wee wee and when she got back inside she was limping. Her left hind leg was in the air. I checked the pads and paw and felt the leg but couldn’t see any swelling, object that’s stuck there or anything that could be wrong. She’s also not crying when I feel and press. It’s now day 3 and she’s still limping. She’s more out and about today. Last night she also moved around more on the bed. Not just lying where I put her. When they were outside (her yorkie brother is 2) she ran at full speed chasing a large bird that was sitting on the grass. No problem. But when walking back to me she hopped along on 3 legs again. Should I be worried?? She is eating and drinking water and barking when the other dogs are barking. Also I need to take her for a car drive that will be about 45 minutes and she’s not too fond of car rides (even though she grew up driving that distance with me). Will she be ok (I don’t want to give her any medication) afterwards if I take her on the drive. Is there anything I can do which will make the drive easier for her? Thanks!