Beef mince (ground beef) smells like vinegar
Probably. Beef should have a faintly sweet meaty smell. An acidic or vinegary smell is never good. I'd chuck it and/or take it back and get a refund, providing it was still supposed to be in date.

With any question of food safety, you have to make the trade off between your willingness to contract food poisoning and the cost of the item involved. Minced beef would cost, perhaps, £5 tops? Which would you rather, lose £5 (assuming you can't get a refund) or spend a few days in bed/in the bathroom being violently ill?