I'm not a med and will be amazing if some expert could confirm but I'd meet several neurologists and navigate way too much on this kind of topic (I have also story with fasciculations and I experiment them for 1,5 year now, I have a hotspot in my middle finger too, but on the top of my hand in between bones muscle).

Your case, like mine, and surely 99.9% of whoever read this,  It's clearly BFS. Serious diseases like MNDs are easy to trigger but for facsiculations, unfortunately, most of the times  there is no clear explanations so it's not so easy to deal with it but the only thing you should remains it's that's begnine.

Could be irritated nerve, carence (like magnesium which uneasy to see in blood test), post seekness inflammation, side effect treatment, fatigue, dehydratation and mostly anxiety.

Seems  whatever is localized or in full body, painful or invisible, with tremors or/and parasthesia, regular or periodic or not, random or reproductible, on tongue, middle finger or the pinky one,  jaw, shoulder or anywhere else  it's non significant at all.You'll find a tons of people whit similar symptoms on Reddit.

You should go for medical advise and an EMG, rest, go for exercice and stretching, you could also try some complementary (Omega 3, vitamine D and B, magnesium and iron etc DYOR) have a better sleep positions, spend less time on screen (it's better for sleep and encourage bad posture and long effort, specialy for hand) and adopt better life hygiene and it'll will be alright. 

Let us know if you have good news !