Me too but that’s a good thing. Means your immune system is responding. Just got mine and knocked me for 48 hours.

I think this isn't necessarily true. The short-term reaction and the eventual immunity boost don't really correspond to each other except in the very vague "a reaction means *something* is happening" sense. The severity doesn't tell you anything substantive. One example reference:

Lack of reaction to the COVID-19 shot doesn’t mean it’s not working | Frederick National Laborat...

You may have had a sore arm, felt tired, or had a headache. Maybe you ran a slight fever. You might have heard these things happen because your COVID-19 shot is working as it should. On the other hand...