Nightfall is very common in young men who are sexually aroused in their sleep or dreams and ejaculate. You can try mastrubation 3-4 times a week before going to bed as a way to avoid nightfall and once yr married and are settled into a regular sex life ur problem will go away all together.

Night falls are a natural phenomena. But when we start having night falls more than 4-5 times a month， then there is a problem. We start feeling weakness， tiredness， etc.. Do not take milk after 3 pm. Try to avoid non-veg， spicy， fried & chilly food. Do not watch pornography materials. Take good healthy diet， do exercise & yoga daily. Take tab. Confido & chandan adi bhati each morning & evening with water. Keep stumic clean & avoid constipation.

This is normal. Nothing to worry. No need of any treatment.