Is my blister infected? and how to stop the pain?

so i was on the beach today, and i had a spade, and i was digging like mad to stop all the water flowing out of a massive hole we had built:L and the spade kinda gave me a blister on the palm of my hand just below the middle finger, i didn't notice it, until i was in some sand, and it stang and i realised it had popped and got loads of sand INSIDE it, so there was nothing we could do on the beach so we put a plaster on it until we got home, then i washed it out, and cleaned it out and got most of the sand out, and put some cream on it, but now its still got some sand in, and its gone all hard, and creamy/clear white and hurts like mad! it throbs and stings and its all red round it, and everytime i move my hand (like now) it really stings:( help?