Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Smut is very sore after running a long distance across fields today. She likely has very sore muscles.
Paracetamol is pretty good at reducing fevers but it's not very good at decreasing muscle pain and inflammation.
Probably a better option is buffered, enteric coated aspirin (like Ascriptin). Aspirin does cause stomach and intestinal irritation and ulceration as well as clotting problems so should not be given for more than 2 to 3 days consecutively and should always be given with a meal. If you choose to use it watch for lack of appetite, vomiting, blood in the stools or dark tarry stools and stop immediately if you see those. Do not use aspirin if your dog has liver or kidney disease or a history of a sensitive stomach or clotting problems.
The dose for aspirin is 10mg to 20mgs per kilogram of body weight orally every 12 hours (about one low dose 81mg aspirin for a 4-8 kilogram dog or half of a 325mg Aspirin for a 9-18 kilogram dog every 12 hours). Always give with a meal. Do not use for more than 2 or 3 days.
Be aware if you choose to use aspirin and it doesn't help your veterinarian will be limited on what they can give as there must be a 5 to 7 day washout period between different nonsteroidals or nonsteroidals and steroids.
You can try muscle massage and alternating warm and cold packs on her painful areas for 10 minutes at a time several times a day.
Make sure to rest her, no running , stairs or jumping.
Please let me know if you have any further questions.