Rapper Big Sean has dodged a big friggen bullet — because he will not be charged with sexually assaulting an underage girl back in August, but he's not entirely in the clear.

23-year-old Sean — was arrested in August during a concert in Buffalo, NY, after a 17-year-old girl told police the rapper and his friend had sexually assaulted her.

Big Sean — real name Sean Michael Anderson — was charged with 3rd degree sex abuse, forcible touching and 2nd degree unlawful imprisonment.

Prosecutors agreed to drop the first two charges on the condition that Big Sean plead guilty to misdemeanor unlawful imprisonment … which carries a $750 fine.

Sean's lawyer Scott Leemon says, the rapper has accepted the terms — and has paid the fine — but still insists "he did not engage in any type of sexual misconduct."

Um okie dokie, then dont admit guilt on any associated charges, uh duuuh!