He wants to suck on those fingers, badly, but instead he just pushes his tongue against them, drops his mouth open further in a soft, wet promise. It's a good distraction from the things Alfie's words make him think- he wouldn't, he wouldn't forgive him, but the fact that Alfie admitted to this makes Tommy's mind reel. He has a sinking, fearful suspicion that he will never be able to anticipate what Alfie will say.