My son accidently kicked me in the back right side of my head and my head hurts on/off since last night, no bump not sore. Eye pain/twitches. Serious?

Bruise. Probably just suffered a local bruise. Use ice packs to the area kicked to help reduce inflammation . Eye twitches are usually the result of general fatigue and not really related to the injury. I can't explain the eye pain from your info - if it persists then get it assessed.