How do I tell my boyfriend I'm ready to go down on him

Samantha • Ohana means family and family means no one gets left behind or forgotten.
How do I tell my boyfriend I feel like I'm ready to go down on him? I tell him I feel ready sometimes but when it actually comes to it I completely chicken out and this is going to sound horrible but last night I was messing about and he was teasing me so I said I'd bite his man parts and I did but I was teasing him and when I did I realised if I did that why can't I go down on him. So how do I say to him I feel ready but also ask him to help me not be so nervous as its my first time