According to TMZ, Nelly was in attendance in a club hanging in a VIP section when someone from the balcony above him threw an object hitting him in the head.
According to the eye witness video captured the moment this happened, Nelly can be seen getting struck in the head with what seems to be an ice cube. After realizing what happened Nelly is then seen charging out of his VIP section towards the balcony, presumably to confront whoever throw the object at him.
According to TMZ the witness said Nelly's team and security were able to intervene and calm the situation down and Nelly was able to enjoy the rest of his night and even later gave club goers a performance.
Check out the video below or on TMZ.