Hello everyone, maybe someone has encountered... My son has stomatitis…

Hello everyone, maybe someone has encountered... My son has stomatitis, and inside his mouth and outside like herpes, it's freaking out, especially at night, high temperature, phlegm How long does it last? How was it treated? What should I do to get rid of this crap faster? The doctor prescribed aciclovir, I understand it's okay on the outside, but can you apply it to the pacifier or cotton swab inside and apply it?