I was playing football the other day and my iPod fell out my pocket and took a hard knock on to the ground. It has cracked but isint like the mirror like cracks, its a extremley thin jaggered line externally (on the glass) from the bottom left to around the middle right. I bought it from HMV and stiill have warranty on it, or should I get a new glass screen put on or should I leave it as it is unoticable when looking at it from above PLEASE HELP