Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern for Noelle.
Typically, lameness issues are going to be secondary to a sprain or strain or even possibly a bruise (which might be something to consider since you found a burr between them)...what we call a soft tissue injury where we seldom can localize the pain or discomfort. However, the majority of these patients are still going to be eating.
When lameness issues are combined with disinterest in food, then there are a few other possible explanations such as tick diseases or bacterial infections such as Leptospirosis.
If you have a rectal thermometer, you can take her temperature. Normal is between 100 and 102.5. If it's high, then I might have her seen. If it's normal and she's not lethargic, then I might give it another day or so.
If she's not vomiting and not currently taking any steroids or nsaid medication, then Aspirin can be given at a dose of 10 mgs per pound of body weight. However, I always advise that it be given with food to avoid stomach upset. If she's not eating, then it may not be wise to give her this drug. You might offer her boiled chicken or hamburg instead of her regular dog food, though, to see if she might find this more appetizing.
My only hesitation about the use of Aspirin is that it might interfere with what your vet would want to prescribe but several doses should be fine.
I'd also restrict her activity for now; I'd only leash walk her outside to relieve herself but no walks at all.
I hope this helps and that you see improvement in her behavior within the next day or so. Deb