7 yr old son has small, light red, raised bumps covering his entire forehead for 2 days & also milder ones on chest as of 1 day ago now.

Possible virus: This could be a mild viral infection causing a mild transient rash along with the lethargy, sore throat, body aches mentioned. If Motrin has not caused problems before, it may be okay to use for fever/headache/aches, but it is possible the rash is related. Try acetaminophen/tylenol instead if ?. If no more serious symptoms, time will cure. If worses, see a medical provider. Maybe contagious.