If it's single episode nothing much to worry but if you continue to have dry ejaculation it may be retrograde ejaculation...During a male orgasm, a tube called the vas deferens transports sperm to the prostate, where they mix with other fluids to produce liquid semen (ejaculate). The muscle at the opening of the bladder (bladder neck muscle) tightens to prevent ejaculate from entering the bladder as it passes from the prostate into the tube inside the penis (urethra). This is the same muscle that holds urine in your bladder until you urinate. With retrograde ejaculation, the bladder neck muscle doesn't tighten properly. As a result, sperm can enter the bladder instead of being ejected out of your body through the penis. Several conditions can cause problems with the muscle that closes the bladder during ejaculation. These include: Surgery, such as bladder neck surgery or prostate surgery Side effect of certain medications used to treat high blood pressure, prostate enlargement and mood disorders Nerve damage caused by a medical condition, such as diabetes, multiple sclerosis or a spinal cord injury..Consult urologist they will help you Regards