My boyfriend while trying to clear his congested nose through spitting had blood in his spit which he drew from his nose. what could possibiy be wrong?

Nothing: Nose bleeds may be anterior or posterior. Anterior are more common in children and can be caused by colds, dry air, allergy, trauma to nose, nose picking, blood clotting disorders can sometimes be problem. Rare bleeds usually self limited and not usually of concern..Posterior nose bleeds are more common in elderly. Probably just single event due to congestion, irritation, and sneezing.

It's usually benign.: Post nasal drip with blood is from irritation and dryness of the walls of the nasal cavity. If it worsens, he needs to see his dr. Take care !