Hello,
Welcome to ehealthforum and thanks for writing
Pain in the breasts can be due to hormonal changes,stress,anxiety or due to too much of fondling.Since you have mentioned that the brassiere was also tight that can also be a major reason.
But it is unusual to have pain after the sexual intercourse.Relax yourself and keep hot compresses for sometime.Take a hot shower bath gently try to massage them.
If the pain persists consider visiting a Gynaecologist for evaluation.
Take care!