Left nipple does not pop out as perfectly as the right. after massage it slightly pops out but not as perfectly, then recedes back. can this be corrected permanently? slightly bothered by appearance. and will it neg. effect breastfeeding?

Common problem: Many women have asymmetric breasts, & many have one or both nipples inverted. This rarely causes any problems with breast feeding; more of a cosmetic concern as you have said. Massaging might help a bit but definitely not a worry. After nursing your baby is completed you could consider consulting a plastic surgeon for an opinion, but all surgeries have some degree of risk (bleeding, infection)