Hi thanks for your question.
Your sister has cancer (type and site not mentioned) and you’re worried about yourself.
One important thing in history you have not mentioned is your age
Your left testis is not smooth and feels bumpy and is different from your right testis.
Most probably you’re having epididmorchitis that is infection of testis and epididmis.
Take a course of antibiotic for a week, and if there is no change in the condition you can consult some surgeon, who will examine you, to determine, whether you have epdidmorchitis or not.
You may need ultrasound
testis and /or testicular biopsy
to know the cause of irregular surface of your testis.
Hope I answered your question