I Have A Red And Irritated Lump On The Shaft

I have a red and irritated lump on the shaft of my penis. It’s been there for about a week now I thought it was a lymphocyte but from what I understand those are painless. I had unprotected sex about 4 months ago with 2 partners but this is just showing up now and I don’t know what to do next. I am 18 and male