Knee still hurts

Hey y'all, this may be out of topic but I was wondering if anyone has experienced this. About a little more than week ago I was at the gym and I worked out more than I usually do. My knee started hurting so I stopped working out. It still hurts today and I was feeling my knee and I felt there was a big bump under my knee cap. I felt my other knee and it felt flatter than the other knee. does anyone know what may have happened before I end up having to go to the doctors?