Having arrhythmia after 2nd dose of pfizer . should i have the booster jab?

Complex, as current consensus states no need if you had both native COVID-19 and full vaccination. Booster suggested for older, immune compromised adults, and immunosenescence does exist in many over age 70. A mild arrhythmia would not be a contraindication for vaccination. Discuss with your doctor, as your cardiac condition may be important here.

If it was not a serious arrhythmia the answer is yes. I am not aware of significant arrhythmias after the vaccine; only rare cases of myocarditis. It is best to check with your PCP or cardiologist who may know more details about your particular situation.