It is safe to take covaxin or covishield by a lactating mother. You might have some pain in the injection site, sometimes mild fever too. In that case, there is no worry, take a paracetamol 650 mg and you can feed your baby. Make sure you take adequate precautions while going for vaccination, like double mask, face shield and keep the distance. Your immunity builds up only after 2 to 3 weeks after vaccination. Take care.