It is a safe medicine that u can take . Do not worry.
Next Steps
It is good that you are scientifically aware that certain drugs may harm the baby while it is being breast fed . The medicine you mentioned is a safe pain medications .
Health Tips
Just make sure u take a rantac tab before meals than take the diclofenac since it commonly causes acidity . Kindly consult if u need any other advice . All the best with your motherhood