Passing any music exam from grade 6 onwards will give you UCAS tariff points, but this isn't relevant for medical school. Medicine offers are based on specific grades in specific A-level and GCSE subjects, plus your performance in admissions tests. Medical schools don't look at UCAS points attained through other things. So no, passing music exams won't boost your application in this respect.
Violin could still be helpful in other ways, though - if you enjoy it. I usually play for half an hour each weekday, and my practice time is a nice bit of calm in an otherwise packed day. It relaxes me and I feel much more focused afterwards. When I was revising for my most recent exam I would grab my cello and play a few vigorous scales every now and then, just to clear my head (that's when I was studying at home, just to be clear. I wasn't breaking out my cello in the middle of the med school library). So if you enjoy learning, keep on with it. You'll need interests in your life outside medicine, things that you do for your own sake and not because they're necessarily going to improve your academic credentials. If you don't like violin all that much, find a hobby that you do.