It is unusual for a common cold to present only with a headache and low grade fever. COVID-19 is a possibility, and a home test can answer that question. However, if headaches persist or worsen, you might need to have that checked out. With the amount of information in your message, it is difficult to come to a definite conclusion.

It could be either - only a covid test would let you know if that is the issue. ? A side effect of the risperdal? - should see your doctor.