HI

One of the testicles feeling tender could be a sign of infection - which is known as orchitis and can present with some burning also .Because the source of the infection is mostly urine.

The fact that your flow is ok suggests that there is no prostate blocking the urinary passage.Also painless ejaculation is also favorable.

But one more possibility is inflammation of the prostate which present with burning and groin pain and referral of the pain to the testicle.

So we have to rule out these two conditions.Urine test and ultrasound scan of the scrotum would be helpful in doing this.

PSA- Prostate specific antigen is blood test done to screen for Prostate cancer and should be done in all males after the age of 50.
A rectal exam of the prostate is also necessary .

Drink lot of water and cranberry juice.Have a nice scrotal support and get these tests done to be on the safer side.Avoid smoking and alcohol and spicy foods.Avoid stress too.

These conditions can be treated with medications and needs to be corrected promptly .otherwise these problems can become stubborn and may take long time to go.

I hope this answers your question.

Regards

Dr.Tharun