Boateng, who plays for Schalke 04, told German magazine Sport-Bild: "Sulley Muntari and I were just joking around and the coach stopped the session and sent us back to the changing room.
"Afterwards I went to the him and asked what he had against me and he started yelling. He insulted me.
"No-one should think I insulted the coach. I'm travelling now and I wish my colleagues all the best for the match against Portugal."
Ghana need to beat Portugal this evening to give themselves a chance of reaching the last 16.