Telling A Joke

Last night, I dreamed of a boy who was shooting at me with a bow and arrow. I got was/became furious and gave him a good beating/thrashing. I didn't stop [the beating] till until he said promised me that he would never do this again. I asked his name before I left leave. He answered,  "Cupid".

Oh, shit! Why didn't you tell me earlier?

(I wonder whether the word "shit" is right to use here. Does it sounds too rude?)  It sounds fine here since this is a joke.