My bitch is pregnant has 4 days left but the set of nipples second from back are hard and swollen i have been massaging them and putting a warm flannell on them could this be mastitis or something else?

Are you sure they're just not full of milk?

thats what i was thinking but i just wanted some more advise, they are abit painful shes not too happy to have them touched but there not red or hot and shes fine in herself, very active eating well and drinking plenty.

I'd just keep a close eye on her then if I was you. I don't think you can get mastitis before pups are born, but with mastitis the teat will feel hot and be very sore and you may see pus from it if you tried to express milk.

Well theres definatly no puss, i have been checking for milk and theres nothing coming out and there not hot.
Thanks for your replies i will keep a very close eye on her.