Thanks for your query.
Read and understood your history of a painful abscess on the thigh and you want to purchase some over the counter medicines.
You can certainly purchase tablet Ibuprofen which is OTC and most of the countries. Take three times a day after food.
Apply liquid Povidone Iodine locally to the whole area to make the skin sterile.
Anyways it is better to report to ER for clinical evaluation, tests of blood and if required an incision and drainage, proper dressing and prescription based antibiotics and other medicines as may be needed.
Hope this helps.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.