Jennifer,
Yes it is possible she pulled a muscle, broke a toe, pulled a nail, maybe something stuck in her paw ... potentially could be a number of things. As a preventative, I'd recommend putting her on crate rest until you can get her into the vet and have her checked out. Disclaimer - I'm not a vet, nor do I "play" one anywhere
. A baby aspirin most likely won't hurt her and I have given them to my own dogs under similar circumstances.
Welcome to the forum and hope Millie feels better soon.
Debbie