Wouldn't be concerned at all tbh, I know lots of people who've had the Pfizer and most had either no symptoms or just a very sore arm, sore muscles and achey joints are also common. Most of the people I know are doctors and medics and therefore relatively younger with a stronger immune reaction.
While not a fixed rule so don't depend on it there is something that can be considered a rule of thumb guide.....generally the stronger the immune reaction, which usually means the less aged the patient, the stronger the likelihood of a short term reaction to the vaccination. The older patient's immune systems aren't usually as responsive or reactive and it can take longer for their bodies to respond.
Important to note that although you'll have some protection straight after the first jab it builds in the following weeks. You reach a reasonable level of immunity after 21 to 22 days and its likely to be maintained at strong levels afterwards. You can still get infected as immunity is not total but partial so carry on with precautions.