Could be scar tissue or warts from the body reacting to teeth of lambs, possibly post disease such as orf or mastitis.
If the teat and udder are soft, not hard or hot, then I would agree with your assessment - she will need a close eye to ensure the lambs are able to suckle that teat, especially to get colostrum, milking and feeding them to get colostrum in if necessary, and then keep an eye they continue to feed as could be prone to mastitis.
If that udder is hard, hot or the ewe is unwell at any time you should call the vet.