Thanks for your query.Based on the facts that you have posted it appears that you have dull aching pain in your left testicle since one week. This could be due to infection of the epididymis
and testis( Epididymo Orchitis ) or due to varicocele
However final diagnosis can be confirmed only on clinical examination and ultrasound
scanning of the scrotum.
Please consult qualified Urologist
for clinical evaluation and further treatment.
This will get cured by antibiotics and anti inflammatory medicines.