Is having somethng like cold sores in the nostrils a bad sign?

No. Herpes simplex lesions can reoccur at any mucous membrane junction with skin. Lips and nostrils are the most common sites. It's just random where (or if) yours show up.
Absolutely. Cold sores are due to a virus and their repetition is a sign that your immunity is compromised. In my experience, the easiest way to treat is look to your diet and take some of the Amino Acid lysine that you can get from a health food store.