The most common cause of irritation of the nasal passages, which is what causes the dried blood, is probably nasal allergies, which are also known as allergic rhinitis. Symptoms that you may have nasal allergies would include chronic off and on nasal stuffiness, runny nose, or sneezing. You may also have symptoms of itchy or red eyes.
If you have any of these symptoms, then it is likely worth considering treating for nasal allergies. Your primary care doctor
can help you with this. To start with, an antihistamine medication like loratidine (Claritin) or cetirizine (Zyrtec) might be useful. Inhaled nasal steroid sprays like fluticasone (Flonase) and mometasone (Nasonex) are also very effective.
You may also want to consider humidifying the air where you sleep with a standard humidifier, as dry night time air can sometimes contribute to drying out of the nasal passages and worsening of this problem.
Finally, avoid picking your nose, excessive blowing, or other manipulation of the nasal passages. Although this might feel good temporarily, it worsens the over all irritation of the nasal passages and will make the problem worse.
Start by setting up a visit with your primary care doctor to discuss your symptoms and potential treatment options!