nice question--how to make your dog throw up!

[DanniYell]

hi everyone, i have a question, we were all out hiking today and my boy mutt suddenly 
comes over gagging and choking a little, then ate a lot of grass all the way back--and 
drank water but cannot throw up, and i know he wants to--he's still gagging a little!  
i think he got something up his nose or stuck in his throat.  a big bunch of grass is 
waiting to come out somewhere!  is there a way i can help him throw up?
thank you!
danielle