Thank you for the query.
As hernia is usually caused by inherited connective tissue
disorder, its appearance in one spot can indicate that in other most common areas the hernia will also appear. One of such places is groin area where inguinal hernia can be present. Such hernia in some cases reaches scrotum and is called scrotal hernia
. It is possible that what you notice as right testicle enlargement is such hernia.
Other possible reason of such symptom are varicocele
which get enlarged due to increased blood flow during the erection.
If it is hernia, the pain should also appear while heavy objects lifting or coughing.
Variocele can be palpated as some kind if noodles in the scrotum.
I suggest you to visit urologist
and have testis ultrasound
Hope this will help.