Hello,
Thank you for your query at DoctorSpring.com
The swelling as well pain suggest that there is some obstruction in the left ureter. The most common cause for this obstruction is due to stones.
I am not really concerned about the pain and swelling but I am certainly concerned about the fever part.
You should see a doctor. Get yourself investigated with some blood tests such as CBC and get ultrasound KUB. Once you have the reports you can upload it for me to review.
However it is better you start treatment immediately after physical examination.
Feel free to discuss further,
Sincerely
Rajiv Goel