Brief Answer:
calculus in the urinary system or orchitis likely.

Detailed Answer:
Hello and welcome to Ask A Doctor services.
I have read your query and here is my advise.

* As per my surgical experience, pain in one side of testicle with back ache
may be indicative of referred pain of calculus in the urinary system as
kidney or ureter most likely with second possibility of acute orchitis (
inflammation of the testicle ).

* Primary concern is to relieve the intense pain with either of following :

- Tablet with content of Dicyclomine or Diclofenac with acetaminophen or
- Injection of Diclofenac or Tramadol hydrochloride if oral tablet is taken and
not relieved the condition or patient preference for faster relief

* Once the pain is stable with above, your primary care provider will guide
you for possible need of an ultrasound of the abdomen and pelvis with
scrotum for the final diagnosis of calculus in the urinary system or orchitis.

Hope this will help you for sure.
Let me know if I can assist you any further.

Wish you best recovery.
Regards.

Take care.
Dr Bhagyesh ( MS consultant surgeon )

---