Twitching muscle (I think) in 3yo's foot

[CookieTramp]

My 3yo is telling me every day at some point - sometimes twice a day - that his right foot is "hurting". When I ask how/where he makes a movement of his hand like something pulsing/twitching. He does get quite distressed sometimes.

I rub his foot and eventually he is ok again, but I have also pressed his foot between my hands and cannot feel anything twitching or moving. There is nothing for me to see or feel. It has been going on for a couple of weeks now.

I googled this symptom and have got myself scared about dystonia, but can't tell if that is something visible or not in the early stages. He is completely hale and hearty in every other way.

Has anyone experienced this? Should we go to the doctor when it happens only once or twice a day and there is nothing to see/feel? Only his complaints and the movement he makes with his hand to illustrate how it feels. I am panicking as I usually do after googling something. I hardly ever do it for that reason but it has got me so perplexed and didn't seem like it could be anything serious.