What are the possible symptoms that could possibly happens if the prolactin level is high?

Prolactin: Nipple (breast) discharge is common, sometimes visual (eyesight) changes, but you'd often not notice this until it got pretty severe.

Milk and no periods: In women, a high blood level of prolactin often causes hypo-oestrogenism with anovulatory infertility and a decrease in menstruation. In some women, menstruation may disappear altogether (amenorrhoea). In others, menstruation may become irregular or menstrual flow may change. Women who are not pregnant or nursing may begin producing breast milk. Some women may have a loss of libido(wikipedia).