It can be just the blood - wash in cold water with a dash of vinegar or lemon juice in it, dry with kitchen paper if it still smells then take it back where you got it. Check fridge temp - this time of year it should be between 0-4 degrees. Keep at the bottom of the fridge to avoid cross-contamination with other foods
Sometimes it will pick up the odour of the plastic packaging or wrapping.I rub it with salt,then rinse in cold water.See if that helps. But if in doubt-ditch it!