If you are having colored mucous , yellow or green, then it is indicative of an infective episode which will need antibiotics. You can have infective episodes even if you are suffering from allergic rhino sinusitis. Blood in the nasal discharge is seen if the lining mucosa in the nose is inflamed ( as is usually the case in infections) and easily damaged especially when blowing your nose hard.
Next Steps
Consult an ENT surgeon for appropriate treatment
Health Tips
Saline nasal spray and sinus rinsing ( jala-neti) will help.