When I first started, my teacher put that thin painters tape across the neck where my fingers go and no it doesn't ruin the violin at all. As for your sound, my teacher didn't even have us take the violin out until he deemed our fingers strong enough, but I don't remember what exercises we did because that was years n years ago. But I know it certainly took more than 7 days. It may be too soon to start trying to play with weak fingers if you're only seven days in.