Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you. I apologize for the delay in anyone answering your question.
The answer is, yes, this could be a sprain. It could also be a bite/sting as you suspected. Given the twitching, this could come from pain, especially a bite/sting. My top two recommendations would be to wash the paw well just in case this is a topical irritant. And second to give some Benadryl (diphenhydramine) at 1 mg per pound every 8 hours, unless he is already on another antihistamine. This will not interact with the aspirin.
Monitor for signs of profuse swelling, bleeding, or pain/discomfort that is really not improving, or true tremors that are not abating after 1-2 hours. These are all indications he really needs to be seen on emergency today. If he is seen on emergency, be certain to alert the ER veterinarian to what medications you administered.
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