Hi ~ my boy was somehow like this too. Also the right hand. We did check with his physiotherapist but apparently they didn’t find anything wrong after checking him. So I guess sometimes babies tend to do things like this out of habit? Do continue monitoring him though, we also did the hand massages daily too and give him bigger/thicker toys to grasp and stimulate his right hand. However, I would suggest to consult your baby’s dr or therapist for the peace of mind 😌
i tend to think it could be a preference thing, I.e. being right-handed. my girl likes to use right hand more, and now has only learned to roll to the right side. I try to put more attractive toys on her left side so she practices that side as well.