Headache from back of neck. It could be?

I'm really sorry to hear that you've been experiencing these headaches and the nasal discharge. It sounds uncomfortable, especially after having a viral infection recently. Given your history of a cold, it’s possible that what you're experiencing could be related to sinus issues, like sinusitis. The yellow discharge you mentioned could indicate inflammation or infection in the sinus cavities, which might also contribute to your headaches. Headaches can sometimes be associated with sinus pressure, so it’s not unusual to have both symptoms together. However, it's important to keep an eye on things. If the headaches are severe, persistent, or accompanied by other symptoms like fever, facial swelling, or changes in vision, I would recommend seeking medical attention. Staying hydrated, using a saline nasal spray, and considering over-the-counter pain relievers might help manage your symptoms in the meantime. If it doesn’t improve soon, or if you have any concerns, please reach out to your healthcare provider for a thorough evaluation.  Take care, and I hope you feel better soon!