Three weeks is still early, maybe you see some improvement with the mucus, but most feel better at 3 months, other sides effects longer, up to a year or more. Erbitux side effects can last a few months after treatment, as well as radiation still working just as long as your treatment lasted, which have acute toxicities, less than 3 months, and long term side effects, longer than 3 months. Are you still taking the antibiotics for the rash? Mine was Minocycline. Still follow the same proper oral care you did during treatment.

Good luck.