It sounds as though you are describing an inflammation of a lymph channel. These run parallel to the flair of the head of you penis, not longitudinalyl The cause of this condition is not clear but these do resolve on their own. Give it a month or two. You do not have to limit your sexual activity. It should decrease in size and go away. If it does not, and especially if it is increasing in size, see a urologist.
S.A.Liroff, M.D