You need to wait until 6 weeks after you’ve stopped breastfeeding. It’s not proven it affects breastmilk but it can affect your healing due to hormones etc, and more risk of infection xx
I wouldn’t get any piercings, Botox, filler, or tattoos when breastfeeding as if you get an infection which is more likely then baby wouldn’t be able to feed anymore till it clears x
I don’t think there’s any definitive answer on whether or not it’s safe, but a lot of tattoo artists would most likely recommend waiting until after you’re done breastfeeding, just purely because of the risk of infection, hormonal changes in your body could affect the tattoo or cause a reaction ☺️