Hey,BenW
In my country they say - "Fear has big eyes". I am pretty sure that when your friend hugged you, you were already anxious and expected a blow. And under the influence of this agitation, you considered the hit to be much stronger than in reality.

Anxiety constantly lies, distorts reality. I went through it myself. Sometimes, the usual touches of my head seemed to me quite strong blows. And when I start to repeat events in my head to analyze the situation, I notice that in my memory this blow becomes ever stronger. Anxiety can overwrite memories, and I’m not the only one on this forum who noticed this. So forget about it. Move on.

If we talk about the blow, I strongly doubt that it was even subconcussive.
Recently, my biology teacher hit me on the head for being sleepy in class. I was so sleepy that I realized what happened only after 3 seconds. And just at that moment I felt anxiety, a slight headache, and dizziness. Only after I realized what had happened,i felt it. After 3 days, everything returned to normal.

Such cases make you wonder. Is it a consequence of a blow or release of stress hormones? I think the second one.
And, most importantly,Ben, do not worry.I think you know that stress temporarily enhances PCS. And,in my opinion, it is the cause of your bad state.

Best wishes,SolisFectum.