Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
It is certainly possible that this thorn could have injured a nerve that is cauisng some of this weakness. It may also be that the bruising caused by this thorn could cause this weakness. It is best, ***** ***** to give Sam aspirin at 5 mg per pound every 12 hrs which will decrease the inflammation that may be affecting the nerve supply or causing Sam this discomfort.
If Sam is stil eating well, this is not an emergency and you can wait until Saturday for your vet to check him.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, ***** *****