No idea what your nurse was on about, but in my country neither me nor anyone I know was recommended to move their arm. And to my knowledge, there were no clotting incidents at all with Pfizer, only with adenovirus-based vaccines J&J and AstraZeneca (and they were extremely rare, although I still was very happy to get an mRNA vaccine because zero risk is better than very low risk, and they have also turned out to be better in almost every respect).